That sounds a little more doable to me. Mind you, I did a 7500 mile trip in 3 weeks, but that was in a car and no kids.
In NY you've got the Baseball Hall of Fame in Cooperstown and the Statue of Liberty for attractions. Many others, I'm sure, but those are the two I'm most familiar with. Boston-Fanueil Hall, Freedom Trail, Duck Boats, Museum of Science, maybe a trolley tour of the city. There's sailing and a jet boat called Codzilla, too. Oh, forgot the aquarium. There are garages that have spots for oversized vehicles-when they put the greenway in after taking down the El trains they took away all the outside parking. You can take PT into the city from some of the outlying campgrounds. Maine is a destination in itself. You've got mountains, coast, shopping, amusement parks, so much to mention. Acadia and Bar Harbor are must sees if you are going to come this far. Southern coastal Maine has many campgrounds and there's a lot of hustle and bustle in that area. Our favorite campground in NH is Danforth Bay. It's not on the coast, but it's a good spot for checking out the White Mountains. There are other campgrounds closer, but DB has a nice pool complex, lots of activities, and is very clean and well run. In RI there's the Newport area with all it's mansions and a nice waterfront area. Vermont is beautiful and more laid back. The Stowe area has a good amount of summer activities. Can't help with Connecticut, though. To us it's a "pass through" state.
Mount Rushmore is OK-I'd spend the time in Custer State Park and do day trips from there. Keystone, SD, is a kitshy, fun tourist trap. There's Badlands and Wind Cave National Park as well.
Your plan is very ambitious, so here's what I'd do. Sit down and prioritize what you feel you MUST do and then things that would be nice if you got there. Concentrate on the "must dos" and work from there. Go with the understanding you won't be able to do everything and if you find a place you want to spend more time in, even though it might mean missing something else DO IT. Be flexible, always have a Plan B and remember that if you don't see everything you want, it's not a failed vacation-it's an open door to come back again.
