It strikes me that life would be a lot easier if each group booking could be assigned a "whiteboard" on a webpage where the organiser and I can chat back and forth, and we're looking at the same hymn sheet all the time.
Sounds like you're talking about a web meeting type environment....
There are some well known names out there, e.g. :
WebEx (
WebEx:Web Conferencing, Web Meeting, Video Conference, Online Meeting Services)
GoToMeeting (
Web Conferencing | GoToMeeting)
As well as countless other me-too solutions (
ProjectPlace ,
Flash Meeting etc.etc. etc.)..... google is your friend.