NeuroZombie
Explorer
My suggestion would be to use the rules as-is, but keep things simple in terms of plot and interaction, at least to start. I taught my step son to play 2e when he was 9, and a few months later 3e came out. I bought the phb, dmg and mm, and bought my step son the adventure game. He ran the adventures in the adventure game before I was able to get something together using the full blown rules, so do not underestimate the mental strength of kids. I sure as heck never will now. My son is now 13, and he growing into one of the best players I have ever played with, and he is in the process of getting the WoTC adventure path adventures together to run (Sunless Citadal, et.al)