Come on man - You and I both know you're already spending stacks on bike parts so why not hook your kid up too. What's $20 if it means your kids looking fly as hell in his/her "My Dad Rides A Harley" shirt. Buy now - cry later. My daughter (6) wears a small and my son (10) wears a large. Shirt color is a slight off white.
Small is 6/8 - (25-70lbs)
Large is 14/16 (75-125lbs)