We Started some drawing lessons based on Mona Brookes book Drawing with Children in September 2012 I really like her "warm ups" especially the abstract design warm up in which someone calls out shapes and types of line and everyone makes an abstract image using the elements I also like the beginning exercises on p 44. There is a grid with a design to copy and a space below for copying. I made a bunch of my own for my girls. I think these two things gave them a good foundation. Then we moved on to representational drawing. We drew lions, hippos, horses, flowers, airplanes.
Abstract warm ups
Warm up grid
Other drawings we did step by step