I shoot photos of my daughters doing cheerlaeding which has to be the worst sport to have to take pictures at due to bad lighting and quick speeds needed and also not allowed to use a flash at all. ...My 70-200 2.8 is usually wide open at 2.8 and the ISO I try to keep low but alot of times 2000 to 6400 if needed for exposure. I have it set to center point auto focus, AI servo, and low speed continous shooting. I haven't tried changing any other settings down in the menu due to not really knowing what they do. Is there some other main settings that would really help with taking pictures such harsh places to take pictures.
One thing that would help would be a faster lens. The 135mm f/2L is often recommended for low-light sports shooting, if 100mm would work there's also the much less expensive 100mm f/2.
In terms of settings, AI Servo is best. You might consider AF point expansion (if the camera can't focus using the selected AF point, for example if the whole AF point is covered by a monochromatic part of a jersey), adjacent points will be used. If you have a fast CF card, you might consider high-speed continuous, as it will likely increase the chance of capturing a good facial expression, etc., at the cost of having more pics to sort through. The other AF settings to explore are the tracking sensitivity (C.Fn III-1) and tracking method (C.Fn III-3). How you set those depends on how you shoot. If your primary objective is to capture images of your daughters, setting sensitivity to slow and method to 1: continuous AF tracking priority. Those settings will result in the 7D trying to maintain focus on the initial subject, ignoring other cheerleaders who move into the frame or pass in front of your subject.
If you don't already, consider shooting in RAW. Although your buffer will fill faster (fewer shots in a burst), you'll have much more flexibility to adjust exposure in post processing, and noise reduction (important if you're going that high with ISO on a relatively noisy camera like the 7D) will be better. Consider DxO for post processing - IMO, it does a much better job of noise reduction than DPP.