Can you tell me if i could give my son a multi-vitamin, mineral, and antioxidant supplement?

Likely fine: If yours is a vitamin family, i see no problem in common supplements. A well balance nutrition, rest and exercise support normal growth in kids. Most of these supplements leave the body in the urine the day they are given. I caution parents to avoid excesses of vitamin a, e, d or k as these fat soluble vitamins do store up in the bodies fat cells and can produce problems.