I was asked to shoot grandparent's day at school tomorrow. The school has setup everything, I'm just bringing my camera and light. Due to it being one family after another I'm planning on setting the camera on the tripod and putting the focus on manual. It'll be two-six people in each photo. Do you think f8 will be enough to keep everyone in focus? I'm using my 5D3 with 70-200 at 70mm.