I wouldn’t go into Boston unless you have to. I wouldn’t get near the coast unless you have to. You’ll start hitting Boston traffic not long after you get on the Mass Pike and it won’t end. You especially don’t want to mess with driving anywhere near Boston Friday or Sunday. The city evacuates on weekends and you could easily need 3 hours to go 100 miles.
Our kids are in Boston, and the last time we were there (car, not RV), we came back from Concord taking 9 to Albany and then hit 90 there. Not as easy as Interstate driving, but not horrible even going through the Green Mountains. We normally take 90 as much as possible, even with the tolls. Much easier driving than 80 and coming from the south.
Boston Minuteman in Littleton is as close to town as I’d get. I stop around Albany and make the last run into the area at midday to avoid as much traffic as possible.
Get an EZPass. You’ll regret not having one.