Elk in Sept. is one of the best times to hunt in pairs or even threesomes.... 
Callers set up 20-50 yards behind shooter / shooters and bring the bull past the shooter. Way better than calling on your own....bulls will often hold up just out of range when your calling solo. That said....I have called bulls in close when solo so it can be done. 
OP, you are overthinking this. (Unless you are worried about your buddy spoiling your spot in the future.) In reality, opportunities with archery elk happen so quickly, the guy/girl closest to the elk (or the one who can out flank the critter downwind) is the one who is going to get the shot.
There is nothing worse than agreeing "Bobby gets the 1st shot" when Bobby is in the wrong place, but Billy could have taken the shot. This is not hunting with a rifle in a wheat field! Whoever is in the best position takes the shot, even if he takes 5 shots in a row. Everybody will be happy with that--or they are not actually "buddies."
