I don't really understand how that would help you. An opto-coupler is an LED paired with a photosensitive diode or transistor. You light the LED like any other LED. That provides current to the base of the photo transistor at the opposite side, which allows current to flow collector to emitter. You would then need to find a way to switch your device on using the current flow. You certainly can do that but you don't get anything out of it. It costs more, opto-couplers are $1+ each. It uses a more power, you need to put at least 10 ma into each LED, so you'd be wasting at least 40ma. With just the fets, all switches on would use 1/2ma with those resistors. It would also add complication to your circuit. When you need to communicate between two devices that need to be galvonically isolated, that becomes necessary in certain situations. Even if you required isolation, since you just need very simple switching action, it would make more sense to just use relays as suggested.