tried-and-true "clean" snack/meal ideas for kids?

We're putting the kids on a super-clean kind of "diet" to try to track down the source of ongoing tummyaches and rashes... they're game, but not exactly thrilled. Trying to eliminate dairy because we already suspect it, plus dramatically cut sugar, and reduce gluten.

Please don't state the obvious - I already know that they can eat fruits, veggies, etc. :o) But if you have some suggestions to offer, I'm looking for tried-and-true ideas for snacks and quick meals that your kids enjoy, but which avoid those ingredients as much as possible.

Thanks!