I would first test with a fronto-parallel setup (a pair of same cameras facing forward, just like human eyes). Then all you need is to calibrate the focal length f and disparity d (i.e., distance between the cameras). Apply blob detection on both cameras to find the ball, and let's say you found the ball center at pixel (xl, yl) and (xr, yr) assuming the origin is at the camera center. Then the ball position can be solved from xl / f = X / Z and xr / f = (X-d) / Z (and yl / f = Y / Z). It's just a simple geometry.
But if you're not sure about the camera geometry, give it a try with Kinect first.