Don't know how close you are to Hartford, CT, but they have a fantastic air museum next to the airport. https://neam.org/
It's not strictly for warplanes, but they are well represented. The last time I was there (a while ago) they were restoring a B-29. Amazing to stand next to it. I notice from the web site that they offer a summer "Aerospace Camp," which might be of interest to your son. Anyway, if Hartford is a reasonable day trip for you, I recommend it.