in no particular order -
watch the sun set from the top of Cadillac Mountain with someone you love....
lunch or a light dinner meal at the Atlantic Brewing Company - The Atlantic Brewing Company's Estate Brewery in Bar Harbor, Maine
- excellent pulled pork, and everything else, not to mention the brews!
we stayed one September 2010 weekday night at "Mt. Desert Narrows" that was just fine - Mt. Dessert Narrows - Sea Breeze, Salt Air, Ocean Views all for you
I'm sure that it is much busier from now through Labor Day. the KOA just onto the island was neat & clean, and rents Airstreams to stay in.
Beals Lobster Pound in Somes Harbor is a little busy for me in high season, but the food is fine and so is sitting outside, looking at the harbor, for lunch.
Route One to or from MDI makes for nice ride. if you take the coastal route, you could make a stop @ LL Bean in Freeport. park in the back lots on Justins Way.
Camden State Park in Camden comes highly recommended by "Over59". we stopped to check it out - looks great!
don't attempt using the George Washington Bridge & I95 north through NYC - take I87/287 and the Tappan Zee Bridge instead.
let us know when you're passing through. we could probably manage courtesy parking for a nite!