Most people want to see the upcoming meeting's agenda. Many would like to influence it or have material to add. So rather than sending email (attachments) to all your colleagues with the details of an upcoming meeting, you should send them a link to the agenda within your WIKI System.
Last-minute changes to the items to be discussed are usually identical for many people. Rather than using copy/paste from word processing software for similar modifications, it is much more convenient for all to collaborate in the definition of the agenda. Also, people who are still traveling could enter new items. Finally the minutes of the meeting can be generated much more easily, as modifications can be done during the meeting itself. More complex modifications could be with multiple persons simultaneously.
If everybody joins forces, last-minute changes can easily be incorporated. Many people start preparing just a few moments before the meeting starts, and the Wiki page is a good way to give them all the information required.
Email all the participants of an upcoming meeting a link to the agenda in your WIKI.