From the sounds of things 200mm might be enough for you. Personally (I know Peter has differing opinions) I would select from any of the 75-300mm lenses and would make sure to get the one with the USM motor. It doesn't make a huge difference with this lens but I always felt like it focused better and quicker. Here's what I'd pick from:

http://www.bhphotovideo.com/bnh/cont...=102854&is=USA

http://www.bhphotovideo.com/bnh/cont...=169267&is=USA

This is the one I recommend:
http://www.bhphotovideo.com/bnh/cont...=169269&is=USA

BTW, Peter's suggestion might also be enough reach for you but it's hard to tell. I'm a little confused why Liz recommended the 50mm. Maybe it was in case you did closup photos.