I would try to make reservations, the rv parks up here are mostly on the small side, and could cause problems with your itinerary.
CT: Mystic Seaport area is worth a stop, the KOA is nice.
MA: Explore Boston, stay Normandy Farms or another high rated rv park.
ME: Acadia National Park is excellent with great biking.
NH: White Mountains/Mt. Washington/Kancamangus Highway/Franconia Notch are all excellent, plenty of rv parks including Danforth Bay and State Parks along the Kanc.
VT: Burlington and North Beach Campground worth the trip, Ben & Jerry's over rated, plenty of better things to do.
Not New England, but Lake George, New York in the Adirondack Park is terrific for biking and hiking and plenty of rv parks.