nh and bar harbor

We have stayed at the Homewood Suites(near the airport) and the Hilton Garden Inn in Manchester. Your teenagers might like the Hilton Garden Inn-it is connected to a baseball field(some minor league team) and it is a unique experience to have a room that looks out on the baseball field. We enjoyed eating at the Firefly restaurant in Manchester.

I wouldn't stay a night in Manchester unless your flight arrives late late in the evening. Take advantage of no traffic and head to Portsmouth or Ogunquit for the night.
Though I don't know if I'd drive "up the coast" to Bar Harbor. The coastal roadways are mostly inland, you don't really see much unless you have plenty of time for detours. I think I'd take the fastest route from NH to Bar Harbor so that you could get up there and enjoy the afternoon, then plan on a leisurely drive on the day you go from Bar Harbor to Bretton Woods, maybe down through Bucksport to see Penobscot Narrows Observatory Bridge, then down through Augusta and western Maine onward to NH.

Most of the hotels around MHT are standard chain places but we've been to the Hilton Garden Inn for friends' birthday parties. They spend the night plus rent a party room that looks out on the ball field so guests can enjoy the game. Manchester has some pretty good restaurants including a variety of cuisines.

Fastest route to Bar Harbor is good suggestion. We usually get on Rt 95 for speed and don't get off for Rt 1 until we're in Brunswick (when we stay in the mid-coast area). Rt 1 gets somewhat scenic as it passes through Wiscasset. Most people aim for lobster rolls at Red's Eats but it may not be open that late in the season. We like the Seabasket on Rt 1 in Wiscasset. Just a family, order at the counter type of place. You should drive thru Camden and then up the auto road for Mt Battie to see the great view overlooking Camden Harbor. Heading north on Rt 1 as you get near Ellsworth you can also eat at Just Barb's in Stockton Springs. Another family, good food type of place. Not sure what you mean by unique restaurant. The lobster shacks are usually closed by Columbus Day weekend since they are open to the weather with picnic table seating. You'll still be able to find plenty of lobster just not the shacks next to the water type of places.
Friends highly recommend zip lining when they stayed at Mt Washington Hotel. Check hours of operation and get a reservation but the peak season might be over by then. You do not have to be a hotel guest.
Weather could be a factor. Nights are in 30s and we usually get a rainy spell as Halloween gets closer. Foliage will be over in mountains by then although you might see some color around Portsmouth NH. Seeing wildlife is a matter of luck. Twice we have seen a black bear near the road in the Sandwich NH area (south of mountains/NW of Lake Winnipesaukee) in the middle of the day. Remember rule of thumb that if you see one deer crossing the road, another is likely to be behind it. This year I finally saw my first NH moose and it was in my own backyard. Wild turkeys are pretty common in towns with farmland since they were originally released in areas with field corn, apple orchards, and good water supply. Eastern coyotes tend to be nocturnal although I've seen them during the day. There's an area north of the mountains called Moose Alley where you're pretty sure to see a moose. Do a google. Your teens might also enjoy a good corn maze. We like the one in Danville VT, Great Vermont Corn Maze which is very popular close to Halloween. It's near Littleton NH so not too far from mountains. We haven't done a night time flash light maze.

Let the teens hike the Precipice Trail or Beehive trail.

thanks for your replies, we have decided to fly into boston and then drive up. should we do the white mountain area first?