I am totally fine with this, but we need to keep coolers out of sight of the bartender. She was a little perturbed last year as she was selling beer inside the event.
As a bartender myself, this can really hurt our income when working events. If you bring stuff, I'd ask that you at least buy something from the bartender, even if it is just a soda, and tip them some. That little goes a long way, and it helps keep a friendly bartender.