If you're going to use high-quality MIDI files and a laptop, Van Basco's MIDI/Karaoke Player would be the way to go, and fire it through your keyboard so you will be using the keyboard's sound engine.

Most TOTL keyboard also provide you with a lyrics function, one that reads .txt files. Those files can be placed in individual registrations, which will display alphabetically, or numerically, whichever you prefer. The same registration can also contain and access a MIDI file with, or without embedded lyrics.

You have lots of options with this,

Gary