Two cameras, Leica M7 or MP, outdoors with slow film, indoors with fast film and available light. Nikon F6, indoors with flash. If you wanted to bring a third, the Rolleiflex on a tripod for formal shots. But, to many camera and you will be spending to much time fiddling with them. The more you use one camera, the controls become instinktive, and you can concentrate on the moment.
JMHO