I would say it's best to teach them the same way you teach them about money. Except for the bits about security. 
Kids are able to pick things up quickly anyway, so it shouldn't be too hard.
I dont think so, children must be playing enjoying their youths, and looking up to be someone who want them to become not introducing a risky system which involves hackers and also huge amount of money, they are too young to recognized the fact that they need money to survive, teach their parents will be a good idea I think, and do you think their parent will allow their child to be at risk?Kids are able to pick things up quickly anyway, so it shouldn't be too hard.