Teaching Bitcoin to anyone is not bad, it's even good because we give them an idea about it. But we know that it is not easy to understand, if those who are old and want to know what bitcoin is, find it difficult to understand right away, how can it be if they are 11 years old, it is okay at that age if your nephew has an interest to know this, determined to know this, but based on your story here you want your nephew to have an idea, your intentions are good, but the interest, determination, and passion should come from your nephew and not you dude.
In order not to waste our time and effort teaching about Bitcoin, we should have to consider these things;
- age of the listeners (must be old enough to understand technical information)
- behavior (must show some interest in the topic)
- we know they can carry high responsibilities in the future
But as OP had mentioned, I actually doubted the result of it. Honestly, it was not the perfect or the good time to teach his nephew.