The first main stage show I did was "Inherit the Wind", which has a bunch of crowd scenes. It was a cast of 32. Fortunately, I had two ASMs, that helped taking down blocking. Each took a side of the stage recording who was coming in from what area and where they were going and I would take down what was happening in the center. Then we tried to sort it out later with who had what. However, even that was crazy getting all of it down. So I brought in my video camera in the rehearsal hall and video taped the crowd scenes. That helped a great deal.
Perhaps this might be a solution for you. However, you might want to check to see if you have permission to video tape it. I was able to do it because I was in an educational theatre setting.
Hope this might help!