Here's how to create a private Admin-only forum:
1. Go to your group homepage.
2. Under the 'More Admin Tools' link, click 'Manage Forums'.
3. Click the blue 'Create New Forum' button.
4. Enter forum name and description (optional).
5. Select 'Group Admins' under 'Who can view posts in this forum', 'Who can add posts to this forum' and 'Who can add replies to this forum' and choose no for 'Should posts appear in CafeMom search'.
6. Click 'Save' when you're finished.