For general things/announcements, the CMS and FB should be perfect. Usually, you put a teaser/blurb about it on FB, and link to here. If you have the stats module installed (I think it is by default on Drupal) you can see just what kind of interest you get by looking at the clickthru's (IIR, Drupal also has referrers, so you can see how much traffic comes direct from FB, or other sources)
As far as the forums go, I'm not sure how Drupal handles them, I ended up dumping Drupal and going back to Firefly because Drupal didnt make much sense to me, but you may want to make a Members only, and an Admins only board. You can use this area to record meeing minutes, or post general ideas for the group to work on. Also, if you're planning on holding events for the public, you'd have to assume that SOME of them may find their way here, and while 'm sure you wouldnt mind them joining, you may not want them to have access to the entire site.
Just my 2 cents though, I'm more used to video game guilds/clans than anything like this :)