I grew up (in the summertime) on an island in Casco Bay. Seven days is not enough time in Maine.
I'm glad to see Red's Eats getting a mention and Campobello Island getting several mentions. My parents retired to Campobello. It is truly a very special place. Make sure to go to the end of the island to see the lighthouse.
Some say the real Maine doesn't start until Washington County.
Enjoy your visit.