It sounds like your son equally bright. Have you considered evaluating BOTH kids for a skip? That would solve the "kids in the same grade" problem, and might help out your son as well -- sounds like he is excelling, and is a social animal to boot. Just a thought.

FWIW, we have had a lot of experience with grade skips in my family (all four sibs in my generation, with additional early HS graduation for my two brothers, and grade skips for both of my nieces as well), and have never been sorry about doing it.