Inside i'd also use studio lights, up as high as I can get them. The trouble will be lighting them evenly. If you're 5m from the front row then you're probably 7m from the back row, so a light in your position will light the front more than the back. If the light's really high up in the air (13-20ft) this reduces the relative distance and will result in more even lighting, unless it falls over, then you're in the sh*t.
I would want to experiment before I did this, take a few friends into the same situation and experiment. Try 2-4 diffused strobes, up high, pointing at them. Try them undiffused too. Try them directly above the camera (you'll be on a ladder), and try having one either side of the camera - 45 degrees or less I think, i'm thinking again of relative distance.
Hopefully someone who actually knows how to do this will answer. I regularly photograph groups of 50-400, but always outside. I only tried it once inside, with speedlites, the photo came out but only ok as no-one had told me in advance what we were doing (original photographer was sick I was the last minute replacement).