Keep your ticket on you. You will have to go back through security. There is a smoking area outside at the back, and you won't have to go back through security.
I have taken my kids to shows there before , and they have concerts like Raffi and Weird Al and They Might be Giants, so I can't imagine they do as a rule. However, if some musicians only want 21 and up as an audience I am sure they would tell you on the ticket or at purchase.
Age restrictions?
Thanks! Your answer is awaiting moderation.