If it's nice and quiet in the middle of a park, away from traffic, put a blumlein rig between them, that would probably be superb...
But if you are on the sidewalk of a busy street, my gut feeling is that omnis and blumlein will pick up too much external noise, and I would concentrate on trying to avoid that external noise. I would use cards (or maybe even hypers), pointed directly at each performer... ideally they are standing side by side and you can run XY/DIN/NOS/AB pointed at them from a few feet away.
I'm not saying I'm right, but this is the strategy I would try first, and probably I would learn something from that so that I would get it right the 2nd or 3rd time.