I would take a yummy IP bar along and eat that while everyone else is munching on not-so-good-for-you stuff. That way you will have something to put in your mouth and get full at the same time which will help you resist all that other stuff. No sense in feeling resentful because you can't have something.
Plus I would also take along some sparkling water. I really like the flavored sparkling seltzer water put out by Canada Dry or La Croix. I especially like the Canada Dry Raspberry or Lime flavors and the La Croix Coconut flavored water.
Hope you have a great time!