There are others with more knowledge about this but that being said, id say a lightning wallet at first until enough has been accumulated to justify a nice signing device like a foundation passport, coldcard or seed signer. The lightning wallet rabbit hole is deep. (Custodial vs noncustodial, kyc vs nonkyc, etc) dive in with your kid and learn together.
Discussion
I think the biggest issue I'm having is how to onboard the lighting wallet , I don't want to use my bank account.... thoughts ?
Ultimately you need to fund your lightning wallet with bitcoin, acquired by mining, purchasing with fiat or earning. You gotta have some bitcoin if you’re gonna pay out those allowances.