In my travels, reading and talking to disaster responders, and my limited experience, I've come to understand that when having drills and training kids you do well to soft-pedal the danger, while not denying it entirely, and make it a game.

If the kids have fun during drills they look forward to them and are open to learning. If you push the danger they get frightened and upset. They cue off of the adults. If the adults express profound fear they tend to magnify it. People have to remember that if it frightens an adult kids, smaller and more vulnerable, have even more to fear. If the kids get frightened the drills become an unpleasant experience they will seek to avoid. There is also the danger that if and when the real thing comes you may have made it so scary that they freeze, hide under their beds, or do other perfectly understandable, but counterproductive actions.

Keep it light. Make it a game. Drill a little bit at a time. Remember that kids have limited attention spans, figure one or two minutes per year of age, and a limited ability to deal with stress. Talking about death and destruction is stressful, even for adults. Kids can be remarkably resilient and show surprising amounts of courage when the day comes but don't wear them out in practice.

You can motivate and scare adults into learning some of the basics and marginally complying, I have my doubts how effective fear really is long term as a motivator, even for adults, but kids tend to shut down.