I am also curious as to what lens and camera you are asking about. The short answer is hyper focus distance. The hyperfocal distance is the distance between the camera and a point in your scene at which everything from half the distance to that point and beyond to infinity will be acceptably sharp.
If this is your first time I would not take on the task for other peoples photos. Both of you are likely to be disappointed. The best advice I can give has nothing to do with the camera/lens. Two things, one, where you shoot from. Location, location and location. And, two, know the sport if you don't you will undoubtedly be out of position for the action.
EB
EOS 1DX and 1D Mk IV and less lenses then before!
