Recently the company I work for was asked to pitch for creation of a forum targetted at children as part of a website solution.
I think that at least we should reccommend
How has anyone else tackled this and what Ideas do other people have on this?
It's not an online forum, but they do discuss some of the things they had to deal with to provide a safe environment for children. Check out the post-mortem of the game team that developed Disney's toontown: http://www.gamasutra.com/view/feature/2027/postmortem_disney_onlines_.php
Think of "online" as being "a crowded place, that contains strangers". Some of the solutions will be the same, others won't work.
For instance, at a child care business at a mall you can require parents to check children in, and the same parents to check them out. This type of thinking will sometimes lead to realization that part of security has to be in the parents hands: you can't "confine" children in an online system, so protecting them from going to the rest of the internet has to be their parents job.
But the idea that every child has a responsible adult is probably a very good one.
Live moderators are probably your best bet. Disney's Toontown actually ran into quite a few privacy/security problems when they missed that kids are often rather clever.
Although I don't know if it's still in there, there used to be a function where you had an "apartment" you could fill with "furniture," SIMS-style, and then display to other players.
So, players intent on subverting the controlled communication would spell out letters in furniture one at a time until a screen name for an uncontrolled chat was communicated. Allegedly, even after that was discovered there was still a system of displaying pictures that worked just as well.
To summarize, you can't cover all the bases. The best you can do is cover the careless and inept, and try to stay heads-up on strange behavior that could indicate somethings up. So if you have to do a "kids forum," I would definitely go with moderators.