Strike is the only one I have linked to a bank acct and that will flow through me for the most part. I did look and cash app allows the user/kid to choose to do the KYC part and from there if they want to transfer it into USD they can. But I'm pretty sure I can give them access to the keys and allow them to buy with sats independently while maintaining my own channel into that wallet for monitoring / tracking. That sounds pretty good to me?