Do the moms become "members"?
If so, I don't think it's outlandish to distribute some literature about the group's policies and rules. You know, along the lines of a refresher document with important information on it such as:
- membership dues and when/how to pay
- activity involvement minimums
- activity schedule
- contact information
- expectations of members: here is where you need to put that "do unto others" type of statement, what the purpose of message boards are, what message board violations warrent deletion, and how if you can't play nice with the group you may be asked to either follow the policies or leave.
Yes, this may insight some gossip but it's a way for you to cover your butt. So everyone knows the Group's standards, and if you can't act in accordance with them maybe the group is not for you. Thus either these 2 moms will shape up or ship out...and if they just get obnoxious, they will know they will be asked to leave.