As an absolute minimum, and assuming adequate clothing and a plentiful supply of water:

AMK Heatsheet
Mini-Bic lighter x 2
Pre-made tinder
Photon III
SAK or small Multitool
Whistle
Mirror
15' paracord


If the kids are responsible enough to go on a campout then they should be required to be on their honor to carry at least this much at all times.