Instead of a lot of compressors, have you looked at a rotary screw compressor? It is much quieter. It can run non-stop. It will give you a LOT of air. I suggest you go to a propane company and ask them if you can buy a 500 gallon tank that is out of service. It will not work for propane, but it WILL hold a lot of reserve air. You could keep that one tank filled, and branch off as needed.
Thanks for all the comments. I have a ton of new props in the works for this year. Trying to make a continuous pneumatic scene that will involve four different props. As for the gemmy skulls takes some time but it isn't that hard. The skull is 4.5 volts(been awhile) you need it to be continuous power so hook it to a voltameter to drop the voltage to 4.5 off of a 12v source or get a 4.5 power supply. The lighted eyes can be hooked to the moving eyes because they run together. The mouth can be programmed via a prop controller or you can add a microphone and adjust the mouth via a wireless trigger. Kids love it Good fun.