Probably one of the bes things to do to teach kids how bitcoin works is to explain them at first how the economy works with something they are familiar with like with candy or toys and then when they understand the basics about the economy then you could teach them about bitcoin.
How do you imagine to explain on the candy child the basics of Economics? LOL!!! With children, you need to speak only at the level of the game. The more economic games with a decent win, the faster and better the children will understand the fundamentals of the economy.
The way to explain something to a person is to do in terms they understand, you cannot explain quantum physics in the terms used by physicist to the average person you need to use examples they can understand, and the same applies to children you need to explain to them in terms they can understand.