MiniDisks use a 3 second 'gap' to flag the end of one track and the start of the next. to do this in iTunes you need a special 3 second 'blank' track to insert in-between the regular music tracks. You can download the track
here
Create the playlist like this:
Track 1
3 sec pause
Track 2
3 sec pause
etc.
What this doesn't do in put all the Track name etc info on the tracks on the MiniDisk, you still have to do this on your MinDisk Player.