May I suggest a back up plan of Bass Harbor Campground? We stayed there with friends in 2011 and the campground is a bit rustic, but has full hookups and great camp owners. Its walking distance to a lighthouse and many trails. We had a great time and spent alot of time in the local area and in Bar Harbor.
We are going again next year and have found the end of August to beginning of Sept is a great time to go...end of season, things are cheaper...even lobster...and after Labor Day it is so quiet!
I know you will enjoy your trip whenever you go...have a piece of blueberry pie for me!