I'd definitely avoid making a big deal out of it being educational or related to school. (Unless their educational experience is very unusual.) This is cool, interesting stuff you're giving them! Obviously, this relies on you being able to sell that idea to the child.
If the direct sales approach seems unlikely to work, you can make it available without much fanfare but give just enough of a hook for their curiosity. (If they're incurious, that's probably the place that'll yield most benefit,)
My parents - I now realise - did a lot of this, "happening" to leave well-written books on subjects they knew I was interested in around the place. So, for instance, leaving books about sex, reproduction and puberty lying around when I was about 11 or 12. We had an adult encyclopedia, which was kept with my parents' serious/valuable books, but they said if I really wanted to, I was allowed to have a look, as a special privilege. So long as I was careful with them and didn't damage them because they were special. So I sat there for hours and hours and days and days with my fingers stuck in the pages, in much the way I do now with browser tabs and Wikipedia.
Also helps greatly if the books are actually good and interesting. The better you know the kid and their interests, the better you'll be able to (a) pick things they will be interested in, and (b) convince them that it is interesting.
I'm finally getting around to reading "Thinking, Fast and Slow". Much of it I had already learned on LW and elsewhere. Maybe that's why my strongest impression from the book is how accessible it is. Simple sentences, clear and vivid examples, easy-to-follow exercises, a remarkable lack of references to topics not explained right away.
I caught myself thinking "This is a book I should have read as a kid". In my first language, I think I could have managed it as early as 11 years old. Since measured IQ is strongly influenced by habits of thinking and cognitive returns can be reinvested, I'm sure I would be smarter now if I had.
So I have decided to buy a stack of these books and give them to kids on their, say, 12th birthdays. Then maybe Dan Dennett's "Intuition Pumps" a year later - and HPMOR a year after that? I would like to see more suggestions from you guys.
It should be obviously better to start even earlier. So how do you teach rationality to a nine-year-old? Or a seven-year-old? Has anybody done something like that? Please name books, videos or web sites.
If such media are not available, creating them should be low-hanging fruit in the quest to raise the global IQ and sanity waterline. ELI5 writing is very learnable, after all, and ELI5 type interpretations of, say, the sequences, might be helpful for adults too.