Setup for including commentators in live stream (including monitoring)
When I first started doing this, I always thought it was better to give them "clean" audio as well. I've since figured out that they want to hear themselves. Also they want to hear each other, so really you do not want a separate feed for them.

Depending on what you are broadcasting, you may not even need the sound from the event.

The only issue you're going to run in with a delay in the video to them commentating is if they are only using the video feed to do it, not the live event going on right there.