Greek yogurt with fruit puree is popular at our school along with wraps.

Our canteen staff cooks a lot of the menu from scratch. Vegi/Chicken burgers, muffins, popcorn, pizza.

Will you be preparing the food yourselves or purchasing?
If preparing you can think about foods that kids love but use ingredients with low salt and saturated fats; like using pita breads as a pizza base with shaved ham instead of bacon, use chicken breast, roasted veggies. Wraps are also a fun alternative.
Jelly cups even with fruit are very high in sugar! Greek yoghurt sweetened with honey and fruit ( fresh , canned, purée) is much healthier.
Healthy dips such as hummus, tzatiki with veggie sticks and crackers.
Instead of potato chips, rice wheels or rice Snacks are tasty.
Sushi rolls are also very healthy or rice paper rolls…hope some of this helps.

traffic light sandwiches, fruity iceblocks,veggie sticks and dip, frozen yoghurt, or in winter, warm custard and fruit, soup, pinwheels ?

Salad in a tub with meat, frozen pineapple rings, wraps, homemade soup, pancakes, muffins, and the good old slinkied apple!