Why buy when you can DIY?
Google Calendar API
Google provides public API's for their web applications precisely because they don't want to bundle and then have to support every conceivable feature under the sun with their service. Besides, with a little effort you could have a DIY calendar utility to schedule gigs with your DIY mbiras. That's cool in a coming-full-DIY-circle kind of way.
From your description, it sounds like you have a semi-fixed list of events that have to get scheduled a certain number of days before or after a gig. So, with a text editor or Excel you could create a CSV file that reads:
"-14", "Mail out calendar listing"
"-2", "Send out email"
"2", "Send out thank you email to attendees"
"4", "Upload drunken afterparty pictures with the strippers to MySpace"
Cooking up something to take this and stuff it into Google Calendar should take around 20 minutes of work. If you're not feeling programmatically inclined, PM me with your email address, and I'll take a crack at it. I don't have much DIY on my plate until Purusha's 670 case arrives (lousy international postage! Bah!), so I'd be happy to help. The only software requirement would be having Python and a few extra libraries to make Google happy. How you go about installing them depends largely on whether you're a PC or a Mac guy.