how well do you know these kids? are they from vegetarian families? Honestly we are vegan (or trying) and my kids would not eat most of what has been mentioned on this thread.
My first recomendation would be to keep it simple.
pasta and sauce are always good.
Tacos with toppies and canned or fresh fruit
veggie sloppy joes with carrot sticks and pickles
frito pie (chilli, fritos and cheese if cheese is cool with you) with fruit or veggie sticks on the side.
(fantastic foods has great inexspensive mixes for all of the above but you could easily make any of them with tomatoes, tvp and seasonings.)
sandwhich rolls are a good way to move beyond pbandj and still have a sandwhich. also because of the way they are made you can disguise all kinds of things in there
spread some cream cheese, avacado, baconaise (vegetarian but with a nice bacon flavor) or hummus and sprinkle veggies and mabey a little fakey bakey for flavor (not if you use the baconaise). roll, slice into wheeles. plan 3-4 wheels per kid. serve with chips and fruit.
tomatoe soup and grilled cheese if you do cheese. really any veggie soup and garlic bread or crackers. throw in some fruit for good measure.
if you really want to go out you can make egg rolls and fried rice. egg rolls are so easy to make and you can stuff them with sheap ingredients like cabbage, carrots, broccoli and garlic. add some soy sauce and ginger for flavor. provide lots of sweet and sour sauce for dipping. fried rice can be done according to any recipe and just omit the egg.