I see.
But you never know; the whole "age limit" ordeal might not be that strict.
Like when my family went to Jeff Dunham last year; ticketmaster said it was an 18+ show, yet my 10 year old brother got in just fine.
The ticket part though. Buy beforehand! Ticketmaster is reliable (I get all mine from there). Or risk this again.
But like I said; I am so sorry, I know that feeling (like All Time Low went to my city, 6 days after my birthday. And I wasn't allowed to go. I cried.)