580ex ii and calumet travelites

[bonnie27clyde]

I am planning on shooting images of a pregnant woman with her 2 1/2 year old and husband. They want to be dressed in white on a black background. I have a canon rebel xti and 3 calumet travelite 750s. What is the best studio setup anyone can recommend? As what light do I use the 580ex ii? The last time I did a portrait session, I used it as the main light behind a white umbrella.

[gonzogolf]

If you have 3 calumets I'm not certain you need the 580. Just put one light in a shoot through umbrella just off the camera and use the other two lights from behind as hair lights.