I don't know where to start
 

My husband and I will be vacationing in Maine (as I've never been) from September 27 through October 2 or 3. We have a wedding in New Hampshire on 9/26.

We love all things outdoors. Golf, hike, bike, beach, FOOD, occasional shopping in cute, quaint towns. But are no means shoppers.

Where do we start?

I'd buy a guide book (or order one from AAA if you are a member).
I'd read everything I could find here at the Destination tab.
I'd search for trip reports and read those.
I'd make a list of things that sound interesting and plan to see those things.
I'd make a reservation for at least two nights in Ogunquit and two nights near Acadia National Park.

So, you have about a week?

The 2 areas most suggested for Maine are the Acadia National Park area for outdoorsy stuff, and the mid-coast area (Camden for instance) for other stuff. Maybe split the week between the 2?

Call up Jeb and see if Big Daddy and Gammy Babs have any room at the inn, in Kennebunkport.

Camden was one of Yankee Magazine's choices for best foliage spots. It's a beautiful town on the coast. In southern Maine, the Ogunquit playhouse is still running shows. Last fall we enjoyed a "class" at Stonewall Kitchen which is really a cooking demo and a great meal served to you in your seats (room is set up classroom style with overhead screen). Surprisingly, no Stonewall products were used. This is in Kittery ME near Ogunquit. You are also close enough to Portsmouth for a visit there. The sandy beaches are south of Portland.

I would see what events are going on you might like to attend. Owls Head Transportation Museum might still have special weekend events. There are sure to be things going on in Portland which has lots of food options and adventures. See if the wine trail might be fun to follow.

Weather is usually great that time of year but cool at night.

I agree with suggestion to split week between two places since southern Maine and mid-coast are very different from each other.

Are you spending any time in NH other than the wedding? For hiking and quaint towns, it's hard to beat NH.