On your camera's sensor, the 200mm would be equivalent to the field of view of a 320mm lens on a 35mm camera, so lengthwise you should be fine, though you might have to crop a bit and you won't be right in the action for shots across the field. I'm gonna say that if you really want to get into shooting sports photography you'll probably have to upgrade. The 75-300mm is a decent lens as long as there is enough light, but it won't track motion very well or focus very quickly.
I would actually suggest something like this:
http://www.amazon.com/Sigma-70-200mm...9978866&sr=1-2
The added f-stop will make a huge difference in increasing your shutter speeds so you can stop motion and the narrower depth of field will also increase subject isolation from the background. The Canon 70-200mm f/4L is great as well, but for your purposes, I would say IS is not as important of a factor because you're gonna wanna work with faster shutter speeds anyways in order to stop motion.