Once contact has been made the only thing that matters is get out of the box and start running. One hand or two hands don't matter. I like what Cabbage said about where top hand ends up and switching to two hands for drill purposes. But once the ball is hit the swing is over and now you transition to running.
If a catcher gets hit then it's the catcher's fault for being too close. I learned that back in the day when my throwing elbow got drilled by a bat on a follow through.
My son, 14u, has been hit twice in the back of the head. Twice the batters have been called out instantly and both team coaches came running for him. In order to avoid it he would have had to have been at least 6 feet behind the plate, that's just not feasible.
My hope is as the kids get older they can swing one handed without hitting the catcher.