Also, I suggest checking out TeenCentral.net for a model of a good support forum.
It is for teens though.
A site which has been heavily modified for ALL ages to safely interact is pottermore.com.
They are also a good model for a kids site. Of course, no real interaction can occur there.
Other sites like game sites and such as riddled with perves and lurkers. I know this from my own experience from when I was a kid. Also, if you have a site for kids, you will get a particularly aggressive spazz attack from time to time...and well, just consider how facebook utterly fails at protecting kids and they only let them in at ages 13+.
So much sticky tape. The kids forum would be great if it was localized. Like semicolon said, for former AFF parents or something like that. Otherwise the risks are incredibly high.