Fast user switching during Keynote presentation

I would like to use fast user switching as a way to quickly toggle between program environments in the middle of a Keynote presentation--by keeping the Keynote running for one user, then switching to the other user to demonstrate a program, then switching back to the original user to continue the presentation. The problem is that Keynote hides the menu bar when in "play" mode, so I can't get to the FUS menu without hitting the "esc" key to exit play mode in Keynote. This is not the elegant and seamless back-and-forthing I was hoping to achieve. Can anyone tell me how I can do this?

MacBook Pro Mac OS X (10.4.6)