I started out with my nephews by scaring the crap out of them.
With gear on, rifles ready, I'd then ask them "how far away is the nearest medic?" "how long will it take to get you to a hospital?"
When they all got good and quiet I'd then tell them "those gun safety classes weren't just for jokes. They're designed to save your lives by not needing to save your life. Act accordingly."
Good times.
