I've been shooting my daughters soccer games for a little while now. I too only have a 70-200 lens, the f4 L version. So I have just resigned myself to waiting for the action to come to me most of the time and then cropping like mad. It's a funny sport. The moment you think a play is going no where, that's when the bast action shots are or a great header or something else important that you should have had the camera up to your eye and on the play, but you just needed a break so you missed the shot. I hate that. It's a none stop action packed game. Unlike football, you know you can take the camera away from your eye in between plays and be fairly safe.
I like the leg extention of the girl in the first image. I bet she drilled that ball. Soccer makes for some wierd leg angles and body motions. Cool set you got there!