Dan,
Wow, you've done some fancy multimedia work here!
I'm afraid exporting MP3 + video would be a low priority for the many new features planned for MidiNotate and the upcoming MidiNotate Composer (
www.notation.com/midinotatemore.htm) Higher priorities in this area are: (1) exporting or saving to the clipboard GIF or JPGs, and (2) exporting WAV and MP3, but without video.
Nevertheless, thanks for your advanced feature suggestion.
Cheers
-- Mark