the games people play
I used to occassionally practice at a private, family-run dojo in Asia. After practice, everyone would go out onto a large deck to drink tea. I was often the last one out because I like to take a shower immediately after practice.
Sometimes the owner's young children would kick their shoes off and come in and run around in the dojo. I would often chase them around until we tired each other out. One day, there was just a 3-year old girl and her mother in the dojo after practice.
When I came out of the changing room, the child was at one end of the room and her mother was at the other end. I slowly started to walk toward the child and she froze with terror. I stopped moving for a few seconds, giving her enough time to collect her wits, and then she immediately ran to her mother and smiled.
She was safe, and she learned how to overcome her fear and move without a word being spoken. From that day forward, she was able to react and move immediately if I ever showed the slightest sign of moving toward her in a meanacing manner. (Just a game we played with each other. When the game was over she would often bring me a snack and sit on my knee.)
Knowing how to react is far better than freezing. Remaining calm, still and motionless is not the same as freezing. It's another kind of reaction, athough more sophisticated than moving immediately. Children above seven can usually instinctively learn to use stillness to their advantage.
The game of dodge-ball is great for teaching such reactions. I highly recommend the game at the end of children's aikido classes. The adults might even have some fun by joining in too!