I don't know if it will work for your needs, but it seems like it might. Best of luck. Six months of consulting with no product. Proves again the rule that today, with software, it is generally better to buy than build. Don't know any Mac programs, but there is a good Mac client for Citrix, which allows for any Windows program to be served up to the Mac, but this is not a small undertaking and sounds well outside your needs.
Technology can be the easy part.
This program has a web interface and is the source of information on campus events that appears on our web page. There are simple and complex and some expense options out there. Ours was selected by a committee composed of the computer center, scheduler, facilities, and conferences. Policy can be the difficult part because any effort to change quickly becomes a political issue. One post indicated that up to 25 people or offices can schedule space.