If you wish you don't need to use real midi Cables , I mean you don't need to run midi signal . If I ware you I'll use Midi Network .
Midi network will transmit MIDI OVER NETWORK .
Also you want to create a network for the 3 machine for remote monitoring using tool like Apple Remote Desktop to be able to change files or just Sleep/restart the Macs .
if you have time to spend on this technology you will see that it come handy for many other purpose .
To start with read this
http://www.soundonsound.com/sos/jul0...cles/tiger.htm