[ravyn]

you could always have the users start off in the COPPA Moderated usergroup and have them only have permission to post in the introductory forum. set the promotion to automatically move them to the registered usergroup after that one post.

If that isn't good, then I think there is a hack. search the mods. I think there may be a product that requires everyone to introduce themselves before having freedom of the board. My way works for me. My way gives me the opportunity to observe the users to ensure that they are not spammers because the COPPA group is set to be moderated by default (but that option can be turned off very easily for your purposes).

Added: I tried to do a search for the hack I was talking about, but I cannot find it, maybe because it is old. I'm sorry I couldn't find it for you. However, there is a hack for vb 3.5 (likely still usable on 3.6) where a welcome thread is automatically started for new users. Here is a link to the hack I was able to find.