The "Talking with Artists" books (Volumes 1, 2, and 3, edited by Pat
Cummings) provide comments by contemporary children's book illustrators on
how they got to where they are today. Each one has a sample of the
artist's early work (sometimes as young as age 5 or 6) and an illustration
from a book. It might be a good tie in to get some of the books the
illustrations come from.
I don't know if these books are still in print; they're available in our
public library. I picked up volumes 1 and 3 at secondhand bookstores.
Another good one is "what do artists do?" (I am not sure of this title...
it is a companion volume to "what do authors do?")