RE: Yotes killing calves?
If traps aren't an option, although they are the BEST and most efficient option, then set up like you said with two or three rifleshootersand have the person positioned in the center do the calling and I'd stick with simple lone howls. By using the howls only, it might be enough to make the coyotes curious as to the "new" guy and also might make them feel that the coast is clear to come into the area before dark.
I'd suggest sitting well after dark with spot lights, but if I remember right, you can't do that legally in the OK state!