What about one of them Visa electrons? They don’t have a security number on the back as far as I’m aware but they don’t allow online transactions. If not, capital one I think do pre paid cards, and so do skrill but guess they charge. I would personally open a savings account, set it as a parent/under 18 one if they can so you wont be able to gamble on it, but will be able to buy online. Check banks, I’m sure I’ve heard of things like these before 🙂