You might rig up a simple parcourse. Have one station where the kids get on and ride a bicycle down and around some cones. The trick on this station is to put on the helmets, use the horn and check for traffic. Substitute in whatever the lesson says.

Get a friend's car, ideally a beater, and the kids have to make sure the two kids in the back seat are buckled in and then get into the passenger-side seat and fasten their own seat belt.

Each station get graded and there is enough of a run between stations to keep the kids winded. Runners are timed and missed points count as time. There is also an age and 'fudge' factor applied for effort and things they knew but couldn't get to do right so a jammed seat belt isn't held against them. Younger kids get a little prompting but older kids are pretty much on their own.

This is one of the things the military does. The mix of physical exertion and memory, after both a class and hands-on training, tends to lock in the lesson.

Make it fun and encourage cheering.