Well, it's hard to avoid Massachusetts if you just want to see those three states, but I can't blame you if you do! LOL
I'd add Maine, parts of Rhode Island (don't blink, you'll miss it! LOL) and yes, even parts of Massachusetts to your list, time permitting.
What time of year are you planning your trip? The coastal regions of all the states have things to offer, as do the mountain regions.
Laconia Motorcycle Week in New Hampshire is June 8-16 this year, if that's something that might interest you.
But campground up in New England aren't usually in "full swing" until the middle of May, and I believe some just open around May 15th. So if you're planning a trip in the new future, your camping options may be limited. But also understand that that campground in New England have to make their money in June, July & August, so that's when things are busiest and rates are highest. Mid-May and September/early October are the best in that regard. But nights can be chilly during those times, and even the days may occasionally be on the cool side.
~Rick
2005 Georgie Boy Cruise Master 3625 DS on a Workhorse W-22
Rick, Gail, 1 girl (27-Angel since 2008), 1 girl (22), 2 boys (23 & 20).
2001 Honda Odyssey, Demco Aluminator tow bar & tow plate, SMI Silent Partner brake controller.