Build a stick of “dynamite” with 7 red road flares. Sand the labels off of them, and tape them together with black electrical tape. Insert a fuse into the back end. You can use model-rocket fuse from a hobby shop. Be extremely careful with this. I have never had a flare light on me, but I always wear a heavy glove and keep the hot end pointed away from me.
When the fuse reaches the end, it will burn out in between the flares without lighting them. Practice a few times before you do this for real! Make sure you use flares that light by friction – not by flame! Pass the “dynamite” around carefully for each boy to hold. Offer to cut a little piece of the fuse off and light it so that they can see it. Let the discussion run its course – the boys should be full of comments.
After a few minutes, make some comment about thinking that you can pinch out the fuse if it’s lit, and then light the fuse. (When I did this, my boys started running and watched from behind their tents while yelling at me to put it out now!) As the fuse moves closer to the “dynamite”, say things like “no, its ok! I can stop it anytime!”
After the fuse burns out, call them back and tell them about the flares. Then explain how the dynamite is like a lot of things in life: exciting, but unpredictable. Compare it to drugs, gangs, pornography.
This one requires some preparation, but the lesson your boys learn will stay with them for a long time.