I've never had problems bringing alcohol back as somebody under 21. As long as you don't have a suitcase full of alcohol and it is clearly a gift, I can't imagine you will have a problem. My plan, if alcohol was found in my suitcase, was always to say that it was a gift from somebody in the country I had come from to one of my parents, and my parents would always have backed me up in that case.

Also, and this is a completely far-off worst-case situation, the penalties for minor possession of alcohol are tiny. Maybe you'd get stricter LEOs at an airport, but you'll generally just get cited under a city ordinance.

Of course, only you know your own tolerance for risk.