You have at least a couple of good choices...
I regularly take my -4 to both the Vineyard and Nantucket. Both are very good to private aircraft - even those as small as RV's. There are excellent bus systems and bike paths on both islands. Bikes are easy to rent. The last time my wife and I went to Nantucket (last summer), the bike rental agency dropped the bikes off at the airport and picked them up there as we left. If you like grass strips, Katama on the Vineyard is a cool place, too. I used to land my Citabria there all the time, but feel it's rough for my RV- mostly concerned about my wheel pants (I should have installed them with another inch of ground clearance). These spots are among the best places to visit by plane in New England. Block Island, off the southern coast of Rhode Island is an excellent choice as well.
PVD is too big and too far from interesting spots to be high on my list. Falmouth is a great little airport, but mostly there for the airport homes on the field. It's not too far from the Town of Falmouth and Woods Hole - where you can catch a ferry to the Vineyard.
Regardless of what you do, you should have a great time. Feel free to send me a PM if you want more info...
Good Luck,
Dean
Bolton, MA