Here is an update:
We're using the mini disk for any music, and iTunes for sound effects (xylophone sounds mostly). The mini disk wasn't that horrible, judging by the fact that we learned how to use it in maybe half an hour during tech week. We have 3 Mini disks, one for each act. We will also be using CD's for preset and intermission
house music.
iTunes is fairly close to being instant (as long as my laptop hard drive doesn't spin down). One of the problems we were facing was that the guy who recorded the sound effects onto the CD put about 1 second of blank time before the cue, so you would push play and have 1 second of nothing, very annoying. Using iTunes I chopped this off, so it responds much better.