I think introducing bitcoin as a story will be better for children to know about Bitcoin and it will be more interesting for them and they would want to get more details about bitcoin as they grow up.
Or you may consider preferring them to watch cartoons of BTC learnings because Kids want to watch a cartoon which should have some good and funny story, any one of them might not make the impression therefore we need a series of cartoons on different big channels so they would get more consumers. Or, we can teach children about how currency is created and from which date we are using currencies, and what types are there.
Questions like these will help them to think beyond their circle of limit, which is that money is there from the start most of them will even think that money is created after many years, this fact will be new to them so when they will have good knowledge about currency and its history they will learn about BTC better.
And with the history of currency, they will know what potential BTC has and how can it become the future type of currency. Everything is revolutionizing even the currencies are.