Bypassing NYC isn't that bad if you do it at the correct time. Stay west of River until past the city.
There is a decent little park near Newport, RI. Melville Ponds in Middletown, RI. You'll be about 70-90 minutes to Boston if you are on a weekend. There are two loops around Boston, I-495 goes wide and 128 is closer in. From Newport to Maine, I took 128 but you have to check traffic and it's time dependent.
There is a nice state forest campground north of Boston that might be an option to drive in for siteseeing Boston. I would find a park and ride location regardless because parking can be even more difficult than driving