Confused Facebook Parent

Today I have nothing to say about PR but I have a parenting question and I hope you can help. As the father of a 13 and 11yr old, I never let them have msn accounts but yesterday they asked about having facebook accounts. I see all the other kids are using their full names and birth dates plus posting photos…so what's your advice? Is facebook safe for kids? Any wisdom you can pass on would be appreciated. Thanks
Wayne (Dad who is trying his best)