There is a game you should try.
All you need is a A4 paper and a friend. One of you will hide his/her face behind the paper. He/she covers the mouth but let his/her friend see the eyes. Then the one who hides the face will try to smile without being seen. I don't know anyone who have succeeded yet. Try that, I think it would give you a quite justified picture of what an andalite smile look like. It's what I've allways imagined it to be anyway.