Why not try the 100-400 mm. It will give you the reach as well as versatility.
Anyhow, this is one of the shots I got at a game recently in India with the 100-400 mm with a 7D. The field was compliant with the International specifications so I must admit that even 400 mm seemed less than sufficient.
I plan to get a 1.4x teleconverter and will see how it goes. I will lose autofocus on the 7D but think it will be manageable because cricket is one game where you can focus manually and wait for the appropriate moment!
