My best advice is to just let a kid be a kid. Playing more is not better. Playing smarter is better.
I strongly advise that kids don't play baseball – or any one sport – all year-round. Young athletes need time off. Their bodies are constantly changing and taking time off helps make sure their bodies are ready to safely play.
Some parents think their athlete should get Tommy John surgery prophylactically and that shows they don't understand the process. Tommy John surgery fixes the wounded ligament, not what caused the injury in the first place.
The elbow is a victim of the rest of the body not working quite right. The shoulder, shoulder blade, lower body, hips, hamstrings – those parts need to be stretched and strengthened. Otherwise, the pitcher will throw through the elbow, trying to create velocity at the end of the throwing cycle. And that creates the injury.