If you have lots of time, I would suggest going north from Niagara Falls and follow the "Seaway Trail" to northern NY. Then, cross Lake Champlain, through northern VT and NH to ME. Route 2 is not a bad ride, and the scenery is beautiful. As far as ME is concerned, again, it depends on the time you want to spend. Bar Harbor/Acadia are beautiful, and after Labor Day, southern ME, Portland south are not crowded. You should not have any trouble with campgrounds, but do remember that some of the more northern ones will start to shut down in late September, early October. Most New England campgrounds close around Columbus Day, but there are exceptions, both ways.
Yeah, avoid 95 as long as you can. But again, after today, the traffic will be a lot more tolerable.
Enjoy your trip - beautiful part of the country you will be visiting.
Neil, Lin, and our furry companions, Ashby and Cody. 06 National Surf Side.