My DS also spent some time on chess kids academy (
www.chesskids.com), there are some lessons and easy games to play.
I really don't understand of the rating my self, I guess the better ones gets, the higher rating. I don't know, what are the ranges.
Also, DS learned all the pieces at the same time, it took him about an hour and he was ready to play. (I personally thought, that chess this early was too complicated to comprehend. I guess it is not.) So I don't really have advice on that. But it sounds like a good method.
Albs,Thanks for the websites, I will check into that.