A 8x8 row-column cross point can address a single relay, pulse it momentarily for a few ms, and then move on to a different relay. It should only take a momentary pulse to fire any given pyro connected to each relay. Each PIC port (8 pins) could handle 256 relays. If you had multiple cross points, say four (using four PIC ports), then you could fire 4 pyros at the same time (within a few us).
At what point do you want to do this using a LapTop rather than a microcontroller?