Campabello (need Visa, it's a long drive),
I think he means you need a passport or passport card as Campobello island is part of Canada.
Depending on what you mean by "fall" will determine how crowded the campgrounds will be. Most campgrounds close by Columbus Day. If you are interested in leaf-peeping you can look at the foliage websites to get when leaves turn on average. This year was not average. We still had green leaves into November. The Cape is the last area to turn in MA-we find that's one of the most underrated areas for foliage.
As far as other sites there's Acadia National Park and the south coast of Maine, White Mountains in NH, historical MA (Concord, Lexington, Boston, etc), cities like Portsmouth, NH, Newport, RI and Portland, ME, north shore of MA (Gloucester, Rockport, Newburyport), Stowe area in VT-there's just so much it's hard to describe it all.