ISO: 100 or 200 (not too much noise)
Most important use f8 onwards (if there are many rows of people)
Camera mode: Manual (if using Av mode, your shutter speed may be too slow)
Shutter speed at least 1/40 - 1/60. (no need very high speed as they will not be moving around much)
Use tripod and arrange the group properly. Arrange in height, also get the rows behind to stand nearer to the front row.
Dreaming... 14mm f2.8, 16-35 f2.8 mkII, 85 f1.2 mkII