For the first 13 weeks of school, we were able to use a freeelementary edition of Redemptive Artistry.
My kids and I had a ton of fun learning about past/present artists as well as their differing techniques.
Shelley West, of Redemptive Artistry, does a great job of laying out and explaining each lesson. Included is a Preschool section, perfect for little hands and short attention spans.
Redemptive Artistry has a facebook page: https://www.facebook.com/shelleywestart/