sushi rolls are no cook but they may not appeal to teenaged boys.

meze plates - they're cheapish you only need leb bread and/or turkish bread, olives, feta, dips, dates and so on. You could provide a bunch of dips and breads etc and give a prize to whoever dishes up the nicest platter.
Is it a Christian camp? If so a meze plate might be appropriate because lots of the ingredients are the same ones that people have eaten in the Middle East for centuries.