50d + 70-200 f2.8 (IS or no IS will depend on your budget)


You will like the speed, flexibility of the zoom in the game, and the reach on a crop body (200x1.6=320mm)


Ideally you need something wide for group pictures, like EFS 17-55 f2.8


With this set-up you will not need the flash using high ISO for all action pictures.