To have the best control, I'd suggest using your Pismo (since you can set-up a dry run at home ahead of time). Stuff always happens in the most inopportune times. Afterwards, you can promise your friend a version in whatever format he wishes.
I'd create it in iMovie and export it as a QT movie (NTSC>Sorenson3>29.97 fps>640x480>thousands of colors), and play it in QuickTime, looping, in "Present Movie" mode (Movie Menu>Present Movie). I'm not familiar with 3ivx, but I'm sure it has the same capabilities.
Set the resolution of your Pismo to 640x480 (in OS9, 800x600 in X) and connect either via your RCA/Composite out (or with the S-Video adapter) or a VGA (DB-15) cable (if using the VGA cable--make sure the projector's resolution is set to 640x480--you don't need to do this using the projector's RCA inputs).
In Present Movie mode, QT gives you the option of playing full screen on black. Downscaling your monitor to 640x480 will curtail any pixelation (which won't be much--even at 800x600). Using the RCA connections, 640x480 is required. (See AppleCare documents #28504: "PowerBook G3 Series: External TV Out" " & #58344: "PowerBook (Bronze keyboard and FireWire): Supported Resolutions for External Displays"). Plug your Pismo into a wall outlet, turn off any sleep or HD spindown options, and you should be all set.
Random thoughts: If running OS 9, apply a lot of memory to the QT (or 3ivx) app. I chose Sor3 codec for smallish size and relatively decent quality. Since the playback will be 640x480 via RCA, the quality need not be HD. Play around with various export codecs (not DV) and see what you like. Try to have a throughout of less than 1MB/sec to avoid stuttering (see this by selecting command+i while the movie is open)
Finally, sound. Your Pismo speakers (nor the projector's, I'd think) will not crank out the dBs. Bring some powered peripheral speakers, or, if this is to fill a room, a Bose Wave Radio will do the trick in a small package.
Have fun.