Howdy. I was born and grew up in Windsor, right there by Bradley airport. Lots of good memories. I think your son would really enjoy "Old Newgate prison" …
https://portal.ct.gov/DECD/Content/Historic-Preservation/04_State_Museums/Old-Newgate-Prison-and-Copper-MineAlso, recommend the Basketball Hall of Fame in Springfield, Massachusetts. Not too far of a drive.
There is a really cool, submarine museum, submarine base in New London/Groton Ct.
groton is really close to Mystic, you could stop by for some Pizza. (try the white clam Apizza).
While you're on the coast, going over to Newport Rhode Island, and check out the mansions. Then go a little farther to New Bedford, Massachusetts, to check out the Whaing museum and surrounding attractions
Last thing I can think of is to look out for any small town volunteer firemen parades. They are usually Saturday nights. Usually have a small carnival to go with them. Very patriotic. Lots of fun. They don't have any dates set yet. But as it gets closer, you should be able to Google it and see if one is going on close to y'all.
Almost forgot, Cooperstown is gorgeous and so much fun. Try to stay at the Otesaga Hotel if you can.