I have a three car garage, and I ran a single circuit to all three openers. I fully expected to have to run a second circuit for the last of the three openers. But, the circuit held when I opened or closed all three at the same time. (added one opener at a time over several years)
I did run a separate circuit for the lights and receptacles.
Are you trying to avoid installing a panel in the garage? The NEC makes it clear that if you run a multiwire branch circuit (sharing the same neutral with two hots) to a detached garage, that it constitutes a single circuit, and a panel (and the ground rods) are not required.
