The interesting way to teach children about bitcoins is faucet site. Just open and give them a faucet site. Trust me , they will enjoy claiming bitcoins. If your child likes playing video games, then give him a gaming faucet to claim. There are a lot of gaming faucets out there. Children will like that. In that way they will be introduced to bitcoins and slowly they will start to learn how to use bitcoins, how to do transactions with bitcoins, its specialities etc.
Yes, it is true, when we think to teach the children than only one thing will come in our mind and that is faucet and also video games of bitcoin. Because children have good memory, if we have a task to teach them, than only few easy things are here to teach the children and faucets and games are best for kinds. But personally, i am not vote for kinds teaching the bitcoin.