As a common rule, children under 18 do not have to show ID at all when passing through TSA checkpoints with an adult.
But airlines could impose their own identification necessities, so your kids might requisite to show evidence of age at the check-in counter otherwise boarding gate, particularly if they look older or younger than they truly are.
If your children are traveling as alone minors, they’re protected by a diverse, rigorous set of rules designed to fight trafficking plus other hazards.