The knitting videos and glossary are really the most informative tools!
And, in addition to that, YouTube has a wealth of invaluable knitting videos.
He also has his Nana for personal consultation and guidance when he gets stuck. Or, maybe knitting classes at a LYS with his Nana?
What more could a little kid ask for?
I'd personally discourage a little 10 yr old from interacting with strangers on the internet, that is, if such interaction is by himself even some of the time. He could pose his questions using his Nana's membership, with her by his side.
That's my 2 cents, for what it's worth.
And yes, I'm a gramma, too. Ten Grands! Ages 3-23!