Mini Disc is an obsolete technology originally created by Sony Corp. The Mini Disc is inferior in sound quality when compared to CD/DAT. Sony Corp. has permanently shelved Mini Disc research and development and it has basically become a White Elephant in the technology arena. Mini Disc recordable media cannot create lossless audio reproduction due to its compression techniques unlike CD/DAT which does not degrade in quality when reproduced, ie., "copied". Mini Disc's are of different dimension than standard Floppy Disk's so you could not use it/them in a standard Floppy Disk Drive. Hence you would be unable to use it/them in conjunction with your Keyboards Floppy Disk Drive.

Laptop computers can play Midi's of course but unless it has a Professional quality Sound Card plus unless they are played through a Professional quality Soft Synth in most cases, eg., Yamaha XG Soft Synths or Roland Sound Canvas, etc., the Midi's will not sound all that good when played back imo. And that is the case even if your Sound System, ie., "Speakers", etc. are top notch.

Playing Midi's through the Keyboard on the other hand; eg., PSR 2000/9000/Tyros/Other Brands, etc., will sound absolutely fabulous if the Midi's are of Professional quality to start with. I would not hesitate to use Midi's in a Live situation with and through my PSR 2000's FDD.

Note: CD's are an alternate avenue to use in a Live situation. The advantages of using CD's is that CD's are Audio files whereas Midi's are just Data Instructions used to trigger Midi events on a Midi Controller Device such as your Keyboard. The recorded audio on a CD/MP3 can reproduce the human voice and all other naturally occuring sound within the ears receivable sound spectrum, ie., (approx. 20Hz-20kHz). A Midi file for instance cannot reproduce Vocals, ie., (the authentic Human Voice) which I am sure you are aware of although a Mini Disc can but there again the Mini Disc is a dead horse that was buried a while back. Your best bet imo is using Midi Files through your Keyboard's FDD or using audio CD/MP3/DAT's.
PS: Please be aware also that to get good Midi sound reproduction through a Keyboard, the Keyboards Sound Engine should be top notch also. You can have the best Professional Midi File made but if your Keyboards Sound Engine is lackluster, so will also be the sound of the Midi file played through it because the Midi File uses the Keyboards Voices/Instruments/Sounds for playback. And that will be the case, ie., "lackluster", regardless of other sound parameters. Hope this helps.

Best regards,
Mike