So then what's the issue here? Honest question. He got birthday money and spent it on things. That's how it's supposed to work. If he then finds that he cannot purchase something else that he wanted because he blew his budget on video games, that's a valuable lesson that everyone needs to learn at some point.

The point is that a credit card is not a proxy for age.

Isn't "prepaid credit card" an oxymoron?