Well, if that's a big win, maybe I can't let this slip away - and I'm not gonna lie, It's actually supporting underage gambling, but of course with a valid reasons as long as you will leave a valuable words to your child not to do it again.
It's a big money and It already happened, your child was already exposed, so what's the least you can do? Grab that money, monitor your child from that day on and move on.
Not sure if there are parents who'll leave that money there, after realizing how much money the child may have lost
afterbefore acquiring that winning amount.