If your children are truly picky eaters, involve them in making school lunches, and be sure to include some of their requests. For example, if they want a peanut butter and jelly sandwich every day, pack it. But make sure to put in a diverse range of side dishes--a peach and yogurt one day, hummus and crackers another, etc.
Have fun packing the lunch--draw a smile with mustard inside a sandwich, or serve things with funny names like "ants on a log" (raisins lined up on a stalk of celery spread with peanut butter). Slip a sticker into the lunch or write a knock-knock joke on a napkin.
If you want your child to be game for trying out new dishes, remember that eating a variety of foods at lunch starts at home, at family dinners. So, encourage (but don't force) the child to try new foods at family dinners. Always have a familiar, beloved side dish (bread, potatoes, etc.) on the table for a child so she won't "starve" if she doesn't like the night's main dish.
But do not be a short-order cook and prepare an entirely new dinner for your child. Your child will not be malnourished from one or even several incomplete meals. She'll make up for it at another meal.
When it comes to lunchbox foods, I'm skeptical of things in cute packages marketed especially for children. Children eat the same foods as adults all around the world. Only in America do we allow so much advertising and marketing to children, mostly of adult foods with extra sugar and cartoon characters added to packages--juices in silvery pouches, yogurt in tubes, etc.
That said, I think it's fine to include one of these popular treats in the lunchbox--there's room for a something with a little fat or sugar in an already balanced lunch.
But don't be fooled by marketers and pay extra to load the lunch bag full of "kid foods." There's no such thing.
-Jennifer Motl