I have no personal objections to a 20 year old drinking alcohol. After all a story my mom told me about my dad's time in Vietnam one of the few things he talked about was he indeed drank alcohol and smoked pot over there. He signed up with parents permission at 17. So my personal opinion if it is "legal" for 17, 18, 19 year old kids to drink Budweiser and smoke pot in Vietnam back in the 60's then surely a 20 year old can enjoy a drink in a Skyclub.
Now the smart saying of just because you can do something doesnt mean you should applies here. OP you have been given some great advice in this thread.