String-O with epunch? Each kid can run several times to try and improve.
I did an event Saturday at a boy scout camp, but most of the kids were cub scouts. This was the first time in my life I've been seriously and repeatedly annoyed at the sound of kids playing. There was so much yelling! Either play is different today, or I'm becoming a curmudgeon.
I really enjoy reading your adventures with teaching orienteering.
If you find something that works, don't worry about repeating it. Even back-to-back. Kids that age like the repetition. So you can stretch a short exercise out by repeating it.