An alcohol free section doesn't prevent a parent from getting drunk prior to the game, nor does it prevent him from drinking during the game. It only prevents him from drinking alcohol in that section & alcohol is not sold in that section.
All he needs to do is drink his beer in the concourse before returning to his seat. The stadium is smoke free, but that doesn't prevent hundreds of smokers from smoking during the game. They simply go to where it's allowed & return to their seats after smoking one or two.