I'm sort of in the same boat you are - my daughter's MDO is going to stop offering lunch starting this summer, so I'm glad to see suggestions, too.
We do go on picnics with our playgroup quite a bit, though, and we've found that a thermos can do great things. A taller thermos is good for keeping hot dogs warm (pop it right from the boiling water, straight into the thermos - if you're worried about choking, just cut it vertically down the middle), a short thermos keeps grapes or cheese nice and cool (and uncrushed), or keeps about six chicken nuggets warm - again, straight from the toaster oven to the thermos.
I also use the smallest containers from my tupperware; one for sliced cheese, one for vienna sausage, grapes, whatever. If this is going to become a regular occasion, you can keep small tupperwares of cheese, grapes, apples (toss in lemon juice to keep from turning brown), or what have you in the fridge, ready for a quick getaway.