Don't leave out the autodidact's shortcuts and specifically mention metacognitive skills, cover rapid knowledge gleaning, resources for hands-on exploration in a topic, how to get the most mileage out of the internet, etc.. That accumulation of top-level skills of knowledge/expertise building would have to be the throughline to make your effort not an alternative encyclopedia. Maybe include a mindmap in each topical section to illustrate the linkages.
Essentially, I'd look at such a book and ask myself: Is this offering my kid something more than a good familiarity with Wikipedia would get him?
