I found the book by Mona Brooks, "Drawing with children", very inspiring, since it introduces children to drawing in a very gentle and systematic way, training the eye to see detail in order to be able to draw better.
In her next book, "Drawing with older children and teens" she explores the ideas further. I really enjoyed the way copying doodles help to train the eye, and even foster new tools for creativity.
That is why I've created my own doodles for my children, and I am sharing the file . Please for personal use only, thank you! You will find 3 pages of designs to copy, plus a blank page at the end to incorporate your own. I truly believe children enjoy things better (and learn more) if they see us enjoying it, too :)