Hi Elizabeth, adding an events function is something we definitely wish to include in a future release of Vantage (planned for v1.2), although we do not have a specific date for when this will be available yet.
In the meantime, it may possible be achieved with the use of a plugin, however AppThemes does not officially support third party plugins, so essentially we cannot guarantee that they will definitely be compatible with our themes. Based on a search of our forums, I see a number of discussions about some of the plugins you mention, but no confirmation that they are working 100% correctly. One such thread you should be able to access is here, with some comments about the issues experienced
http://forums.appthemes.com/ajax-event-calendar-34129/. It's possible someone has been able to get these plugins working and just not mentioned it here in the forums, but if your intention is to purchase Vantage purely to use the plugin, it's not something we can clarify for you at this time. Thanks.