The first time I became interested in this whole surviving in the outdoors thing was when I talked with a search & rescue crew that was running a booth at the local county fair. His recommendations were almost dead nuts what Doug Ritter's Survival for Kids link describes.

Ever since then I've been a proponent for small lightweight essentials kits like Doug's PSP supplemented with shelter, a knife (for all but small children), a first aid kit (sized for the person), and a small light of some kind. I'm just not into big heavy kits or big heavy knives.

My choice for a cheap lightweight multipurpose shelter is a pair of bright orange 55 gallon trash bags for adults (I'm big, so I need a big bag), and smaller 30-something gallon trash bags for kids. In addition to providing shelter the second trash bag can be cut open for a larger signal and can be used as a ground sheet. In an emergency it can even be used to pack out trash!!