Danni,
I was 18 when I had James, and 21 when I had Madeleine... I was very mature also and had been for most of my life.
I can honestly say that had I been given a decent amount of money at the age of 18 or even 21, the money would not have been spent wisely. It most likely would have gone on a car, travel or something similar for my kids. So, I guess even if Madeleine was mature, I would still want to wait until she is older... I would prefer for the money to be used as a step toward a home