I give this speech to parents every year in our summer camp program. There are many things you can pack for lunch that will stay good up until they eat it. Children don't need HOT lunches; and most likely would prefer them at room temp or cold depending on the climate they are in.
I pack my boys things like:
baked chicken nuggets, chicken patty sandwich, fish fillet sandwich, hamburger, hotdog ,etc...wrapped in foil. It will not be refrigerator cold when they eat; luke warm rather...so no bothers.
I'll take a glad bowl and put mac and cheese, spaghetti, lasagna, cooked carrot rounds, corn, YOU NAME IT... in it for a side.
AND LEFT OVER PIZZA?... kids love that!!! Don't even warm it in the microwave the next morning... straight from the refrigerator, foil it up and put it in the lunch box. It won't be cold by the time they eat lunch.
As for packing yogurts, gogerts, cheese sticks, pepperoni slices, and things like that... you can preserve and protect them by FREEZING a capri sun or Kool-aid (we keep several frozen in our freezer)and using it as an ice pack w/the foods that need to stay cold.... by the time your child eats lunch, the food is good and the drink has thawed to a point they can drink it! Then they don't have to bring back and forth a heavy ice pack either!!!
As for juices... there are 100% juice packs on the market now.. I would stay away from soda; encourage water bottles, you can refill water bottles w/the crystal light packets or some powder drink packet too.
YOU HAVE A LOT OF GREAT responses here on your page... bottom line I'd have to say... toss out the idea of "typical lunch for kids". Rather think about the USDA pyramid and what a well rounded lunch would be: One serving from the protein group...used to be meat; now protein: meat, egg, cheese, nuts, yogert, etc); two servings from fruit/Veg group; and one serving from the bread group.
Have fun and good luck!