If I recall correctly, we stayed at MT Dessert Narrows campground whee we did Bar Harbor. It was several years ago. Don't remember anything bad, and the lobster was good!!
Couple things I remember:
There is a land bridge you can drive across at low tide, stop and look for shells, etc.
There is a great lobster pound right at the causeway
Acadia National Park is beautiful - we did a lot of hiking there
On the way out there we came across Penobscott Narrows Bridge. There was an old bridge (it's been torn down now) and the new bridge has an observatory in the top of the tower. I'm a Bridge Engineer, so I couldn't pass up stopping to visit.
That's all I could pull from the memory bank...