Thanks everyone! Here's what I ended up doing - I showed my own example as a model, but also said that we're all unique and so everyone's picture will be unique, etc. I suggested starting with a circle for the head. I also emphasized that not everyone is an artist, including myself! -- And that's OK. Provided lots of encouragement as they worked, and it turned out that the boy who was so concerned about "not being able to draw people" did a truly fantastic job!!
Some great ideas here for the future, so thanks again! I love the idea of finger paint - it's almost "expected" that the picture would be a little messy and thus, imperfect. I am a new teacher though, and need to ease my way into the fingerpaints! I can imagine that fingerpaint-day could be one chaotic day.