CAMom -- Don't know if your dh is swayed by research:

http://www.davidsongifted.org/db/Articles_id_10017.aspx

If your ds is making friends now, he'll likely be just as socially adept and make friends among the kids who are a year older.

And I don't see how he's going to be held back in playing sports. If he's pretty good, he'll play all 4 years anyway ... I don't understand that. Boys mature at such different rates.

What a frustrating situation for you guys. :-/