plenty of the cereal bars you already mentioned, we also take cup a soups and pasta and you can now get pot noodles in a packet much easier to transport. if you dont mid carrying tins then tins of tuna an ham or cornbeef and take some pitta breads or deli wraps. all keep well in all temps really. take plenty of pittas and then a bag of chips can be shared.

i dont really have my thinking cap on atm (bloody kids stressing me out arghhhh)
im sure others will have ideas.