[racket] running thirty copies of DrRacket from one user account?

I've got a bunch of visitors coming in tomorrow for a DrRacket Music demo, and I'm hoping to have them all use the same account. My experience with this in the past suggests that there may have been some contention over prefs files; some machines became unresponsive, and I'm guessing this was the issue.  I took a quick look through the docs, but I don't see any way to make prefs read-only.  My guess--right now I'm compiling and don't want to touch the system--is that making the prefs read-only will mostly work but require clicking away a bunch of dialogs. 

Am I missing something obvious?

Many thanks,

John

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