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 do not think that you should really teach your kids about Bitcoin unless you really see that they are interested and ask you about it all the time. Kids are able to pick things up quickly anyway, so it shouldn't be too hard.
But if they do not care then let them focus on sports and school because those two are more important.
But don't ever teach them on how to earn bitcoins, because when they try to learn how to earn bitcoins while they are still kids, possibly that their earnings are going to be used in gambling.
And even worst if they are really curious and they are able to search about deep web, maybe they are going to be involved.