I've been a teacher since 1996. IME, parents who complain about school functions should stop complaining, come up with ideas to make things better, and then volunteer to help.
Here's an idea: Use some common sense when planning your event. That's about all it'd take. Honest.
It wasn't my event. It was your event. You use some common sense. It's harder than just complaining on a message board while hiding behind an alias, but it's also more likely to produce worthwhile results.
The burden of proof normally rests on whom ever claims that a statement is true or false. Therefor you both have a unmet burden .The burden of proof is on the dude who's doing the challenging.