You accomplished your goal in this piece remarkably well! I highlighted above the one part that stopped me. The challenge of quantum mechanics is less "prediction" per se and more that it violates our assumptions about how reality works. In other words, our model of "if x then y" is flawed. But I don't know how to explain this to a kid, or even that you can. (Didn't Feynman say that if you understand quantum mechanics then you really don't?)