I was thinking what you were thinking, a timer, or even wireless remote, I know focus might be an issue but i can just fill up the CF card and see what i get.
i also may go to the 70-200IS lens so i can step back a little further.
It really amazes me how sensitive some of the kids are. Now its anticipation from some of the kids. I mean its not like i am right in their face. some of there " little" movements are so fast--it really is like sport shooting.