Manchester to Acadia ,Maine
 

Leenabug,
I live in Maine so I think I can help you with this.

Cape Neddick and Lighthouse is a very popular spot for photos, and attracts lots of visitors. There are 4 beaches in York so you can spend some time walking the beaches. Hike Mount Agamenticus in Cape Neddick if the spirit moves you, about 800'. Pretty easy hike, 360 views.
About 5-7 miles north on Route 1, or coastal, windy, scenic Shore Rd. in Cape Neddick, you will come to Ogunquit. VERY popular and with good reason. Walk the Marginal Way (coastal walk, gorgeous), and has a gorgeous sandy beach that stretches forever.
If you have time, hop over to Kennebunkport for a coastal walk.
Portland, Maine's largest city, has plenty to see and do, restaurants, museums, commercial waterfront.
I've never been to Harpswell, so can't comment.
Wiscasset is a small town, famous for Reds. There really isn't a lot to do there, except maybe walk through the village. That would take about an hour or less. Red's is always busy, but the one and only time we stopped there, we weren't impressed.
Boothbay Harbor is about 15 miles off route 1, and has a nice harbor. (Camden's is prettier IMHO). Still it has nice shops and waterfront, but the main reason we go there is to visit the Coastal Botanical Gardens, well worth the detour. Not sure what will be in bloom in October.
Bar Harbor and Acadia National Park. Well worth several days, if you're an outdoorsy person. Lots of hiking, spectacular scenery, biking on the carriage trails, canoeing, etc. Nice shops in BH, as well as the much smaller Northeast Harbor and Southwest Harbor. In NH, you might hike up (our you can drive) to Thuya Gardens, small but pretty. Thurston's in Bernard is famous for it's lobsters and it sits right on the harbor. Parking is a pain though.

As you know, you will be coming up during foliage season. Be prepared for lots of traffic.

Enjoy Maine.

Ok, so if you have to be back in Manchester for Oct. 9th, you really have 5 days.

So, I guess I'd head our early Sat AM and visit Cape Neddick, Ogunquit, KPort and spend your night in Portland. If you have time, you could stop at Laudholm Farms, a saltwater farm, now a nature preserve/museum where you can take a nice walk from the farm to the sea.
Day 2-Portland-art museum, maybe a boat ride to one of the islands, lighthouse.
Day 3-visit Camden, Boothbay Harbor, and surrounding seaside towns. Maybe Coastal Botanical Gardens. Maybe take a schooner ride from BH or Camden, hike up Mount Battie in Camden. End up in Bar Harbor in Acadia NP.
Day 4 & 5-Acadia NP. Back to Manchester late morning/ early afternoon. It will be a long ride back to Manchester. 5+ hours.
The Manchester airport is small, I'm guessing that you wouldn't need to be there 2 hours in advance.

You could fly into Portland, it's also a smaller airport. From Portland to Cape Neddick it's about 45 minutes south. So you'd be driving south to visit those places, then heading up north all the way to Acadia, then back to Manchester.
On the other hand, since you are visiting southern Maine, those would be on your way from the Manchester airport, more or less and no need to backtrack from Portland to Cape Neddick, and back north.
Take a second look at a map, and judge for yourself.

I always take an early flight out of MHT and that time of day is very busy. Not sure how busy for a 7pm flight. It's a fairly small airport so I would either have a late big lunch or an early dinner unless you want fast food at the airport. (There is a full restaurant but I've never eaten there.) Check MHT website for how early they think you should be there.
Get an early start Saturday morning. You shouldn't have a problem with Rt 101 east to I95 but I95 is going to get congested early. The big advantage of MHT would be the chance to stop in beautiful Portsmouth. We usually go east to the coast from Concord NH via Rt 4 and connect with I95 at the Portsmouth traffic circle. The drive is prettier but you are going thru towns. Rt 101 is a boring limited access highway. Up to you but Rt 4 goes past Wagon Hill Farm and then connects with Rt 16 and a pretty approach over the bridges. I always call it Great Bay but I think technically it's a different body of water.

1. Cape neddick and nubble light house
2. Portland head light house
3. Giant stairs harpswell - this is a short coastal walk which I like a lot better than the Marginal Way in Ogunquit but you'll have some driving to do. The Harpswells area is very rural which we love. Double check what restaurants might be open in October. Our favorite lobster shacks close before the end of September. You have to go thru Brunswick which is a pretty college town. We recently stayed at an air b&b in Topsham but it was just over the town line. But being a college town and October it might be a college weekend when hotels are booked. From Brunswick you'll go thru Bath. Take a look to the east when you go over the bridge for a glimpse of the Bath Iron Works. They are probably working on a huge Navy vessel. The crane is enormous.
4. Wiscassets waterfront and red eats lobster rolls: Wiscasset is a pretty little town but you don't have much time. For the first time ever we stopped at Reds in late June when there was hardly anyone in line. I'm embarrassed to admit they serve a great lobster roll BUT I don't agree with a Maine relative that it's worth a 2 hour wait in line. Even the short line moved very slow on the day we were there since they don't have many people working in the small shack.
5. Boothbay harbor: I'm torn about Boothbay but the Coastal Gardens are beautiful. Maybe not so great in October so considering the miles to get there I would skip Boothbay in favor of little Rockport which is north of Rockland. Rockland has an industrial working harbor but there's a nice place to walk in one area. Rockland is also a large city. We like Claws on Rt 1 if they are still open. View of the harbor isn't so great but it's a Maine kind of place. You might consider the easy short hike to Owls Head light. No view unless you walk up the stairs.
6 camden: I would end your north bound trip here. It's probably the most beautiful coastal town in Maine and very upscale. Don't miss the auto road up Mt. Battie. We like to sit awhile up there and look at the water. I don't think you have enough time for Acadia and Bar Harbor unless you are rushing through. There's a lot of inland miles between Camden and Acadia.
7. Acadia National Park
8. Bar harbor
9 . Maybe take a different route from bar harbor back to manchester and see the shaker village?

Given an overnight in MHT and a stop in Portland, I might choose Brunswick for an overnight. There's a lot of restaurant choices. Camden is about 1 1/2 hours away so it depends on what you want to do between the two. You might check into what's going on at Owl's Head Transportation Museum for the weekend (east of Rockland). Last summer we split our week between the Rockland area and Brunswick but it was over 4th of July and we wanted to go to the 4th of July parade in Bath. If you choose to go to Acadia then I would aim to stay in the Camden/Lincolnville area but it probably books up early.
If you decide to see Canterbury Shaker Village make sure you have time for a guided tour. You can take the route west from Portland which my sister thought was just as quick as going south to Portsmouth and then west on Rt 4. It's very beautiful and you might want to visit some small local places (i.e. Fox Country Smokehouse) and stay in Concord NH for the night. Color in this area has already gotten a good start. You could have one last ride to Warner NH and a drive/hike up Mt. Kearsarge. Hop on I89 then south on I93 back to MHT. But from Concord to Warner take the back state road thru Hopkinton and Contoocook. (follow signs to Concord hospital and then keep driving west). A stop at Gould Hill Orchard will give you a last view of the distant mountains and some great apples. They make their own hard cider but probably don't have a tasting in the morning.

In regards to saving $170, have you also checked car-rental rates in both cities? I would book soon as cars sell out in early October, or get really pricey.Also there is lots of traffic late afternoons heading to Logan, and also getting to Manchester. Portland may be worth it just to avoid any of that.

Airfare will jump up if you wait much longer to book, too.

Choose where you'd like to go depending on what you want to see and do. Rocky coast? Beaches? Mountains? Lakes? The current foliage map is predicting that you will have color most everywhere. Lodging is probably easier to find, at this point, on the coast....but if you stay somewhere like Ogunquit or Portland you can easily take full-day drives out to the mountains and lakes and foliage.

The advantage of going north first is that I93 is very scenic. I always choose to take I293 which connects with I93 north of Manchester because I293 takes you on the west side of the Merrimack River and you can see the beautiful old mill buildings on the east side. Those buildings now house offices, colleges, restaurants, museum. Going north you start to see the mountains in the distance and eventually I93 goes thru the White Mountains. Color is later on the coast which is warmer. You could stay in Concord for the night and visit Canterbury Shaker Village which is just north of Concord. Get a good map because you can take back roads or get off exit 17, visit the village and return to I93 at exit 18. There's a nice orchard Apple Hill near exit 17 which has a small farm store if you want to choose some baked goods, apples, etc. for your trip.

All the Concord hotels back up to I93 but the Marriott at Horseshoe Pond is next to a nice walking area where you might see some wildlife. The Holiday Inn is within walking distance of the lovely downtown area. Stores don't stay open late but there are restaurants on Main Street.

But if your visit the the White Mountains means going on a weekend, I wouldn't do it. There are plenty of other beautiful places to visit without all the traffic. Color is already beginning in the Concord NH area. An occasional tree is already very bright. Still a lot of green but some people like the mix. You can easily head north and take the northern route thru Bangor. Google maps says I93N to Rt 2 to I95 August Maine to Bangor is almost 5 hours. If you get an early start you'll be ahead of foliage traffic coming from MA. You'll see some of the mountains. A long drive made even long with stops for lunch and dinner but you could be in Acadia the same night.

Friend says mount Washington a must
 

Bring a coat! You can check weather conditions at the summit when you get here. The problem is changing plans if weather is bad. We live in NH so were lucky enough to decide when it was a perfect, clear day, to go for a ride on the Cog.

I would choose Camden as the prettiest place to visit on your list and it's right on Rt 1. The drive up Mt. Battie auto road doesn't take long and the view is incredible. You can have a nice drive on Rt 1 going south and get on I95 in Brunswick. Keep in mind beaches north of Portland tend to be rocky. Beaches south of Portland tend to be sandy.

Boothbay Harbor and the Harpswell area require some extra driving time since they are off from Rt 1. The southern Maine coast is very congested but if it's a weekday, travel on Rt 1 might be ok. Acadia might not be miserably crowded this time of year. Camden might be but mostly shoppers in the downtown area.

Unless your flight is early, I would not spend the night in Manchester but do figure on a lot of commuting traffic in the morning. An hour ahead should be enough time to get there but since you are returning a rental car I'd add 30 minutes.

I was at the Grand Staircase in Harpswell yesterday, and was completely unimpressed. Difficult to find, and a very short walk along the coast. And since you are stopping in Ogunquit, and hopefully walking the gorgeous Marginal Way, I'd skip Harpswell.

Also, on day 7, of your second itinerary, since you will be in York (of which Cape Neddick is part of) you could take a walk on the Fisherman's walk, which goes along the York River all the way to Harbor Beach, or you could do it in reverse. It's about an hour, is flat, and very scenic. Easily doable, as Ogunquit to Portsmouth in total is only about 15 miles, so you could fit it in on your day 7. And you can drive up Mt. Agamenticus (or hike) off Rte 1 in Cape Neddick for 360 degree views.

should I bring all winter clothes?
 

Yes layers, very chilly at night.

From Ogunquit, drive along Shore Road to Cape Neddick it's a nice little drive.

Definitely bring layers including short sleeves plus sweaters or long sleeves.

BTW I have lived in VT for 35 years and have still not made it to the top of Mt. Washington. It is hard to plan in advance for a good clear day. You can have a great trip even if you don't do that.
As others have said the weather varies a lot in the Presidential range. Definitely check on conditions before you go.

The problem with the Cog is to get a guaranteed seat down you have limited time at the top. It's ok if you just want to look at the view. But, if it's foggy or raining, there might be nothing to see. One time we took the Cannon Mountain Gondola to the top. It was a free day for fathers day or something and we were doing to do the ride. It was foggy and we couldn't see anything. There are many other things you can do if you don't go to the mountains. Shaker Village would be a good tour even in the rain. It's already spotty colorful in the Concord NH area but with cold nights (36 last night) color might start coming on faster. If your planning to go to Acadia via Bangor, we liked the Cole Transportation Museum which was more about work vehicles instead of classic cars and planes like Owls Head. Winslow State Park in Wilmot (close to Concord) offers some nice views with possibly a lot less people/traffic but it's a much smaller mountain than Mt. Washington. A rainy day alternative would be to visit the Kearsarge Indian Museum in Warner. https://www.yelp.com/biz/winslow-state-park-wilmot
You are sure to find some fun and color no matter the weather but I think avoiding congested traffic and crowds is key.

You could use this site to check for conditions on the top of Mount Washington. Things can change pretty quickly so I wouldn't rely on any forecast a few days out. In addition to fog you could encounter high winds. The mountain is known for having very extreme weather.
https://www.mountwashington.org/expe...n-weather.aspx

The Canterbury Shaker village is really an interesting and beautiful site. As dfrost says, color could get much more advanced this week. This foliage tracker should be helpful. It also suggests scenic drives.
https://www.visitnh.gov/foliage-tracker