Yes this is the book I was thinking of!!!

So true. I bought this book for my little one a few years ago. It follows a similar approach: Barter > Shells > Gold > Fiat > Bitcoin. 

https://www.amazon.co.uk/gp/aw/d/0578490676

398ja

I think there are bitcoin learning materials for children 

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bitcoin_beginners

Resources for Kids

Before teaching them about Bitcoin, teach them about the history of money. In their way of understanding or even in form of a game.
You will never truly understand what is bitcoin if you do not start with what is money.