DS8 read books 1-5 just as he was about to turn 6 (in KG). I had read the books and did not feel comfortable with him reading 6 and 7 at that age. He read the whole series at the beginning of this school year (so he was about 7.5) and it was fine.
We have only watched the first 3 movies because DS feels they leave too much out and change too much of the story smile