I have to agree with htirwin. By all means give the kid access to learning resources, and if he shows interest in something specific then encourage him to take it further.
I think a healthy imagination is invaluable for many reasons, including this quote
"If you want your children to be intelligent, read them fairy tales. If you want them to be more intelligent, read them more fairy tales." |
-Albert Einstein.
At his age I would seriously recommend a crap-ton of fiction. Bedtime stories can go a looong way. Off the top of my head (trying to think in the right age bracket) I would recommend the works of Dr Seuss, and Grimm's Fairy Tales (see if you can find the complete works of both).
In a few more years he maybe introduce him to Harry Potter, Terry Pratchett's Discworld series, The Hobbit, and The Lord of The Rings. I'll also give an honourable mention to Joseph Delaney's Spook series.
You don't have to limit yourself to these books, if they get read, go to the library (or bookshop) and get some more.
If you want to read to him you might want to look up some basic voice acting techniques.
In terms of actually teaching him things I can't think of any specific recommendations, but you should be able to find some good education activity books/video games. I remember as a kid "playing" a safari video game, it was kind of like an interactive David Attenborough special (without Attenborough), I don't remember what I learned from it but it was loads of fun.
Anyway, good luck with creating a genius child :)