A wise scoutmaster friend told me once that boys join boy scouts for three reasons; 1. to Build Fires, 2. to Build Fires and 3. to Build Fires. I'd opt for more fire building and debris shelter building sorts of things. These are hands on which will keep the kids busy and keep them from getting bored. Have them build a fire, then cook lunch; build a shelter, then sleep in it overnight, that sort of thing. Also, maybe assembling personal survival kits and then using the kits in your demonstartions.