If the banquet is being held at a restaurant again you can call the restaurant and ask for something to be set aside for you.
I always carry one or several of these things with me: gluten-free crackers, kind bar/think thin crunch bar/bakery on main bar/simply bar, nuts, gluten-free granola, fruit, bag of sugar snap peas. I'm constantly on the go, so I end up eating at least one meal a day out of my purse.
I personally wouldn't trust bar food. I stick with wine and bring crackers with me.
I went to a wedding recently and mildly glutened myself on some appetizers that the caterers thought were gluten free (I should have been more careful). Couldn't eat anything for the rest of the night and was feeling not so great. I'd say better to have your own snacks if the caterers aren't 100% positive that their food is safe. Just hold onto a glass of wine and take small sips all night. And remember that while food is a factor at social gatherings, the most important part is enjoying good company