Coach or first name?

[Texas Aggie]

I will refer to a coach by their first name if I know the first names of both coaches.

This is bad advice. I know the first names of 80% of the varsity coaches around where I work and I would never call any by their first name on the court or in front of any other coach. I have 2 pretty good friends that are head coaches that I talk to semi-regularly and even if they played each other (which would be odd, since one coaches boys and the other girls), I would still address both as "Coach" on the court.