I would go with a belly band for the boys. Don't tell him, but sometimes I put Teddy in a diaper at home.
Check out my site and if you are concerned with poopie accidents, PM me and I can sew you a special lined diaper and make it for you in a "BOY" fabric so that we minimize any chance he might be made fun of by the other kids
(Teddy just wears our standard designs, mind you).
Good luck!