I had an issue with my nuttyX taking our child in situations which have 'adult' content...no, not a Bar, AA meetings.
Trust me, the things that are said there are waaaaaaaaaaaaay worse than what you'd hear at a bar!
My argument was the adult content she was exposed to. The judge agreed~ he is no longer allowed to take her to his meetings.
If the 'Bar' also serves food, it could be a hard battle to win. If it's just a Bar and does not allow minors at any time, for any reason~ it is clearly inappropriate...the problem is, as other posters mentioned, PROVING the child was there. And when, and why and for how long.