Thanks everybody. The speed was 1/30 sec. ISO 800. Lens 70-300 f/4.5. I played with many speeds and 1/30 gave me what I wanted in terms of movement. 1/60 could give more detail on the faces but that was not my priority; it was movement.
Now, using flash, impossible. It was a huge theater and photographers were only allowed behind the last row; no flashes were allowed. It was close to 15 of us there taking pictures.