Hmm, okay, overall, yes, it's true that minors are strictly prohibited from gambling. However, if the situation is as you described, OP, where a child wins big without their parents knowing and then needs personal information to withdraw the money, then I would allow my child to use my personal information. The reason? Because it would be pointless, even if I didn't provide my personal information at the time, my child would still be suspected of gambling and thus be able to win.

I'm not killing two birds with one stone, but that's a significant amount if it really happened. And perhaps after I successfully withdraw it, I'll tell my child that it's an activity that shouldn't be done by small children. I know the warning might not be effective, but after that, I'll give my child my full attention.