I'm going to do a Boston-RI trip b'h in mid August, the plan is to leave Tuesday night to Boston staying there over Shabbos & then head to Newport RI sunday morning, I plan to take a tour of the touro shul, check some mansions & do the cliff walk (as much as I can go with a stroller) then leave Sunday night back to Brooklyn.
can I do all this in one day, is it worth staying another day, am I missing out on something?
You can def. make another day worth it on the way back. Consider a Touro synagogue tour, Newport harbor cruise, cliff walk, and a couple of mansions for day 1.
For day 2, consider Mystic aquarium, USS Nautilus submarine and museum, if the USCGS Eagle is in port, it's a great attraction (ask for more info at the Nautilus) and for a relaxing trip home try the Cross Sound car ferry. (New London, CT - Orient Point, N)