Bitcoin is difficult to explain. I also felt difficulties in understanding bitcoin for the firs time. Let's share how to explain bitcoin to children of teenagers. In My country I can say 98% children don't know bitcoin. In fact, bitcoin can be future money. If the children not familiar with cryptocurrency or bitcoin, how can they face the digital era in the future.
I'm not quite sure if Bitcoin is appropriate for children and teenagers but in terms of explaining how it's functioning it should be easier then to other groups. They are more familiar with new technologies then older generations and they addopt informations easier and faster.
But I wouldn't let them into cryptocurrency word before they are 18.