C.J.
What about overnight camp? I went to camp for 28 days when I was 7 and LOVED it. Depending on the type of camp, it could be come a "thing" for him:)
other thoughts are season passes to things he likes to do (zoo, children's museum, etc.)
I am with you about experiences vs things.
If you need some suggestions for summer camps - start with the American Camp Association listing of what to look for and a list of accredited camps.