Funny story about that.

When I was a kid, 15+ years ago, my parents told me about somebody that did that here in Texas with their son.

The father took his underage son to a restaurant and was able to get him a beer. During the meal, the father went to the bathroom and the son took a drink of his beer. A cop was sitting nearby and arrested the kid for underage drinking because the father wasn't in the presence of the son so it was no longer "supervised".