Legal Question in Employment Law in California

They are too young to legally be employed under California child labor laws, but I can't think of any reason why they couldn't serve as volunteer sports referees if their parents or guardians consent, and the participants agree to abide by their rulings. As a practical matter, these junior refs would face a risk of injury from the game itself, not to mention the risks posed by nutty parents, and others, who sometimes get into angry confrontations with sports officials. Do you really want some bozo yelling, "Kill The Umpire" at a 12 year-old?