I worked with 4-5 year old preschoolers this last year and I have to say, not a single one of them would be able to understand, appreciate, or sit through any of the CoN. We spent the year learning to share, take turns, ABCs, etc. In my humble opinion, reading them the Chronicles would be like feeding a baby a steak. They couldn't digest it, much less appreciate it.
I'm sure many of you have brilliant 4 and 5 year olds who can do calculus and read all seven books on their own, but the ones I worked with (my own two kids included) are not so privileged. Of course, in a country that values test scores over intellect and celebrates mediocrity over excellence, I could expect no less.
But don't get me started, don't even get me started...