Just focus your cameras and use your DOF preview you lazy bums!
Just kidding of course!!!
By the way, the 1/3 in front, 2/3 in the back will become very apparent very quickly, and is a very, very useful phenomenon to learn about and take into account. The first time you try to shoot three people in a row, lined up at a 45 deg angle to your plane of focus, you will really appreciate it!