I can't really add much more than has already been said but learning to pan with the models and be smooth when you use the camera is a good technique to master and might help with this slightly.
Have you asked around with the racers and seen if they object to you using flash ? I don't know how the track and rostrum is set up for you but I'd imagine if you're facing the same way as the guys on the rostrum the flash isn't going to blind them and will to them be quite lost in the hall you ran in so I don't think it will affect them. If you don't ask you don't know ?
Post up how you get on though this is a really good thread for people wanting to photograph at their club
