MIDI data is like a musical score, so the information will all be there, but the others person's machine may interpret the "closest instrument match" to play the audio (i.e. their instrument sounds may/will sound different). If the intent is to have them modify the MIDI data, then it is simplest to send only that. The "audio" that they hear will be good enough (in most cases) to work with.
As example, here is a straight up
MIDI file I last touched in 1999... clicking on it in your browser will play your browser's "best interpretation," but you get the idea (the SONAR version is VSTi loaded).