We were up there last fall. One stop for sure is Beth’s farm market. We enjoyed a windjammer sail boat ride out of Boothbay. If you hit a rain day, a trip to L L Bean is an interesting place. 
Be aware a cabin is normally pretty rustic. There aren’t many straight roads in Maine and point A to point B usually means going around water to get there. 

I would definitely go back again. 

Chuck