A lot of comments saying they will provide the data to get the big money :;
Absolutely, some child will hide the winning if the child knows his Dad does not support his gambling habit, and if the child has a solid relationship with his Dad, then the decision to provide such data is sure.
To me, it all depends on the relationship parents had with their children. No matter how you advise the child not to gamble anymore after providing the details for withdrawal and it was successful, the child has already developed the urge to continue gambling, but such parent should be careful enough because the addiction may increase rapidly.
That's our responsibility as a parent, to advise, to manage/control and to help him to get out from gambling because he is still underage. For the winning, if it is something that we considered as a huge amount or a life changing amount, I will not let it go so I will help him to withdraw it but once it is withdrawn then I should keep the whole amount. Starting at this point, I will give more attention to what he does.