I make my living shooting sports. If you have a few minutes you can check out my site at www.thepicturedesk.ca.
The 70-200 2.8 is a great lens, on a second body for indoor sports like basketball. If you plan to provide great shots you will need either a 300 2.8 or 400 2.8. I used a 400 and 600 combo when I shot with Nikon but when I switched to the Canon MC II a couple years ago I went with a 300/500 combo. It's a bit lighter, cheaper and Iamb getting old.
I wouldn't consider a long zoom, they're just not good enough. I would leave the teleconverter at home as well.
Just one guys opinion.
-Rob