I do this for my son, too. Here is what he eats:
PBJ on whole grain.
applesauce. I buy a big jar and portion it out.
Yogurt. Big jar, too.
Cut up fruit.
Cut up carrots, celery, and cucumber. With a little peanut butter to dip.
"Trail mix". Basically I get sugar free dried fruit and mix it up with cereal and goldfish.
String cheese.
Whole grain crackers and cheese.
I don't get lunchables because of the salt content and also because it's cheaper to make your own with better quality cheese, crackers, and meat.
I have found (to my surprise) that he will eat just about anything I send, even if he wouldn't eat it at home. i.e. the chopped up veggies. I think it's because everyone else is eating and he doesn't think about it. He's at an age where he "doesn't like" veggies. Only with me, though. Sighs.
It won't hurt to send the same thing all the time. They still will eat it.
Good luck!