Good luck, medicating your child can be a very difficult personal decision. My advice is to familiarize yourself with the potential adverse reactions, know who to contact should one occur and also how long before you can expect to see an improvement. Keep us updated on how he (and the rest of the family) are adjusting.
Every kid reacts differently to medications, but I want to give you a little hope. I have two kids who take Lamictal with very good results and virtually no side effects. Just start low and go slow with the titration to avoid the rare risk of a rash.