We would like to use team calendars to track and report on where team members vacation, sick leave, etc.

Consider providing functionality like contentbylable or reporting integration to allow the contents of one or more calendars to be minded and filtered.

A complete solution would allow users to enter their absences (sick, vacation, etc) into a team calendar and then extract this as a report every two weeks that would be past to our HR / payrole people. Combine this with associating labels (separate issue) to filter events and you have a powerful solution that can be integrated to other systems without API programing.