Hi C.,
Definitely check out AAA and gocitykids.com. There are also several children's atlas/travel books that you can get for your kids so they can learn about the states you are going to Rand McNally makes a few. (Check Amazon or Barnes & Noble). We go to Connecticut twice a year to visit my husband's family so we have lots of things to recommend:
1) Mystic Seaport and Aquarium. The Aquarium has Beluga Whales (which you don't see often and my son loved them - he is 5) and last summer they had a rare Stellar sea lion. They also have lots of other animals and dolphin and seal lion shows. The sea port has old ships and shops and whaling museums.
2) Essex Connecticut Train and Steam Boat. We went on a cool train ride (they gave the kids a list of things to look for) then we went on a Steam Boat on a beatiful river.
3) Norwalk CT has Stepping Stones - an interactive children's museum.
4) RI is pretty close to Massachusetts. You can go up to Boston or go to Plymouth Rock. If you go up there you can also go to Martha's Vineyard for the day - they have multi colored houses and lots of fun shops. You can rent bikes and drive around the island.
5) Connecticut and Rhode Island have lots of farms - you may be able to do hayrides, pet animals, pick fruit.
6) If you like the water, there are Whale Watching or other ocean trips.
I hope this helps! Have a great trip.