I am assuming the 30d will work the same way but I know with my 40D I can tether it via a USB cable and the Canon software. As I recall you can config the setup to save the shots locally as they are taken. If you setup a 2nd display attached to your laptop you could then put up the shot w/o a need for people to move around or, even more important, want to reach out and fiddle with your laptop. Anyway, you could then have something set to monitor that directory for new files and automagically open on the 2nd display by extending the desktop and moving the preview window to that display. Depends on how you prefer to make it work.
It is my experience from running demos for clients, there always seems to be one or more in the room that "knows what they are doing" and wants to press buttons to prove it. So, I started dragging around an external display, even before there were nice light and cheap LCD panel displays. Then I kept the laptop setup where they could not get their grubby mitts on it!