Clever. But have you considered you may well be committing some form of assault, which may in turn invite a lengthy prison sentence, and expose you to a tort action that may result in your having to fork over all the money gained?
Best bet is to take the fingers off the kids menu, and give your server a sizable tip with your newfound wealth. If they won’t let you order off the kids menu because you’re too old and unaccompanied, splurge on the adult selection, but deduct the amount from your server’s tip for their being so difficult.
Do not take the server’s fingers. That would be wrong, even if they refused to let you order off the kids menu.