He's just a couple of my initial thoughts, you need to find a way of dramatically reducing the time to produce the finished image, both in the taking stage and in the PP.
At the shoot stage, you can try and maybe take just three group shots, so then your only working three images. If you can use a tripod and make the background static, carefully place the folk within each individual shot, again limit the number of shots to cover everyone, you could simply then merge the images in PS. This takes just a few seconds, a bit longer to set up at the shoot stage, but will still save lots of time overall.
In Lightroom you can create many different presets, which you can apply with just one click to various elements of the image production without compromising any quality.