f 9-13 is generally recommended for larger groups to get everyone in focus, but if lighting is dim and your OCF is not enough to cover everyone, you might have to go to f 6.
200-400 ISO will give you the cleanest images with the least amount of noise and noise really matters if you are trying to get a lot of faces into one shot. Again if you have to step it up due to lighting challenges, make sure you know what your camera can handle. An old Canon EOS 5D Mark ii will show grain at 400 ISO, but a Canon R6 will still be fine at 1000 ISO.
a rough "general" ISO guide:
ISO 100-200 - full sun
ISO 400-800 - cloudy & dusk
ISO 1600-6400 - evening & indoor
(12,800-25,600 - dark)
shutter speed & flash
know your camera's sync speed (it's probably around 200); start there to test your lighting. With two strong OCFs and a fast shutter, you will avoid that motion blur that causes soft-looking images.