Turn IS off for sports or your pictures could be soft due to the IS not being settled while you move the lens and press the shutter.
Then, keep your shutter speed high to freeze motion.
Unless you are trying to do something fancy like use a slow shutter speed and pan with the subject then use IS mode 2. In general turn IS off for erratically moving subjects.
I have a 70-200 f/2.8 II and shot with a 5d mk iii which I know it'a a bit short for soccer and football, but would you suggest the same in my case?