We live in NH and frequent many campgrounds in the general area. The campground in Acadia you want is Smugglers Den in Southwest harbor. Many sites have a good amount of room between them. You have a choice of cement pad pull through, and back in gravel sites. Trolley service to everything in the area runs through the campground every 30 minutes.
I have hosted and attended rallies in Acadia on 5 occasions. Our sixth will be in August 2018.
Others have already said it, you need to be in New England late september early October to catch the fall colors.
I will be happy to share links to campgrounds we have stayed at and found to be good in Maine that are as far south as Berwick and as far north as Rangely and Bar Harbor. I would also suggest checking Campgroundreport.com for unbiased reviews of any recommendations.
I can tailor the links to cost as well. We do a lot of resort places, but small mom and pop places and KOA's.
Short List:
Flat Rock Bridge
Gray Family Homestead Campground (Driving challenges getting to this but its beautiful)
Wassamki Springs
Desert Of Maine
Freeport Durham KOA
Bass Harbor Campground
Point Sebago Resort
Bayleys Camping Resort
Powder Horn Campground
Wild Acres Resort
Narrows and Narrows Too Campgrounds
Bar Harbor KOA(s)
These are a few.
Eric