When should I use activities vs. events?
Jon -

If you use events to track your attendance, you actually get the benefit of both (since event registrations also generate activities).  :-)  Depending on your version of Civi (which unfortunately you didn't specify), you may be able to create your event as a recurring event.  You could then import your attendance lists (assuming of course all your attendees are already in Civi; if not, then you'll need to import the contact info first, then import the participant records).  

My thought is that if you go ahead and go the route of events, you're already situated to take online registrations down the road if that becomes a need, and/or to register people in advance and then send scheduled reminders.  I think that going the activity route might work quite well in the short term, but prove limiting in the long run as your needs and use of Civi evolve.

Hope this helps,
Lesley