The kids like the easy, less messy things:
Donuts,fruit,breakfast burrito,and cereal.
Pizza,nuggets or chicken strips.

Of course Nachos(can't have a tourny w/out them)
Big hunks of beef jerky go over well.

We sale "Walking Tacos" at our school concessions and they go over very well! In fact we sale them for $2.50 and it only costs about .50each to make them. We always sale out! To make them you put corn chips in a bowl, top with taco meat,cheese,lettuce,onions,jalapenos(option).