One book my kids keep coming back to over and over again is Mark Kistler's Draw Squad. They got this book out again this morning and sat happily going through lesson after lesson. I didn't have to do anything except look at their page when they excitedly told me to see what they were able to draw.
Sophie by far is my most artistically minded kid. She loves to draw and is usually the one who checks out the drawing books. The other just give sketching a try now and again.
Ian is creative just not with the medium of pencil and paper. His medium of choice at the moment is legos. His online art class has really challenged him. He needs more formal instruction. I think we are going to need to have Ian go through the first few lessons of the Draw Squad too. So he will feel a little more confident in his drawing ability.