The -2/3 ev is exposure compensation, used with either Av or Tv or P. It tells the camera to override the exposure it calculates by (in this case) 2/3 stop. Normally we use exposure compensation when the overall scene is naturally darker or lighter than mid-grey and we are trying to render the colors more realisticly.
For stopping action, 1/500 is usually enough, especially with a wide angle lens. So I agree with Charlie that you would get better results (wider dynamic range and shadow noise) if you're shooting at your native ISO which is 100.
So for shooting action outside, ISO 100 is usually fine, even in shade. Set your mode to Tv (shutter priority), exposure compensation to 0, shutter speed to 1/500, AF to AF-servo, and you should be fine.