Moos and Frost can agree to the specifics of the deal without directly meeting. Everything can be done by 3rd parties, which sounds like most of it has already been done.
I know Moos would prefer this wait until after this Saturday, but there could be a very small chance that UCF pushes the timing of things up. It's probably unlikely, but they could feel like a jaded lover. I don't know how old you are, but in March 1989, Michigan's basketball coach, Bill Froeder, had accepted a new coaching job with Arizona State effective at the end of the season. Bo Schembechler, who was Michigan AD at the time, basically told him to go to ASU immediately. Michigan named Steve Fischer the interim head coach, and they won the National Championship by going through the NCAA Tournament.
I am not saying that this will happen in this instance, but if UCF asks Frost "Do you want to take the NU job", and he says "Yes", they might just tell him to go immediately.