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.