The Rock?
I don't think he could play a below average size, egotistical and cunning 13 year old.
Now for the main cast: no one you can name.
Seriously when you see that kid from some other series, so much gets killed in the new role.
For special characters sure, but for the stars no.
For example, I'd love to see Morgan Freeman as the Ellimist, that'd be sweet.
And I think Christopher Lee would be perfect for Crayak, things like that