We took a similar trip two years ago. We were most interested in the lighthouse.
http://www.visitmaine.com/attraction...rs/lighthouse/ My favorite is the "Nubble", Cape Neddick, but at Pemaquid you can go climb up inside. we flew into Boston, spent first night at a hotel near the airport. Rented a car and went north along the coast. We had reservations at a little motel in Rockland, Maine. One day's trip from there will get you to Acadia and Bar Harbor. One day we went to Augusta. The last three days we stayed at Nantasket Beach Resort near Boston. Not really close to Boston, but it was right on the beach and not very expensive. We took a day and rode a bus tour of Boston. We didn't see much color in the trees as they were having a heat wave.