Healthy concession stand ideas

What about whole grain tortilla chips and salsa?

Organic Fruit Leather

There is the "obvious" fresh fruits and vegetable - apples, bananas, celery and carrots.

Maybe you offer popsicles too but they are made from real fruit juice and no high fructose corn syrup.

Greek and Lebanese foods are very healthy and easy to cook on the go. You could offer items like Pitas and Chicken Shawarma. Those meats can also be used in salads.

Another idea would be to sell rice-based dishes like stir fry and other Asian non-fried dishes. This allows you to load up fresh vegetables and other healthy options.

Fresh, locally produced fruit cups produced as part of the previous day's prep work come to mind.
Additionally, I'm becoming more and more fond of the almond-it makes great almond butter and can be ground to a meal and used in place of flour and cornmeal and is a very low-carb alternative.
If you feel that you must sell a sugar-laden product to attract the youth of this land, consider using ground Stevia root as a sweetner, instead. It's great tasting (with only a very mild aftertaste when over used0, makes a great conversation starter and seems like a good image/brand developable concept.

Try a smoothie stand with fresh fruit smoothies, or grilled chicken sandwiches, maybe even Pitas, or subs. Have some healthier finger foods like apple slices, and granola "bites". Hope this Helps :D