Make up...

What is a good age for girls to wear make up??? I have two girls (10/7) and don't have a clue. I know I don't want them to start when I started, at the ripe ole' age 12.  What were my parents thinking? I was still a baby.  I think I can hold if off a bit, just due to the fact that they are home schooled.  No pressure from other tween girls. Is 15 or 16 a good age?  I am really conflicted by this, my girls play dress up with make up and when Vanessa (10) comes out with her make up on... I am thinking "Ya, you're NEVER gonna leave this house when you get older". What should I do....???