Event lights configuration Fisrt Time doing this

been invited to take pictures from time to time in a ballroom.... so far I dont have a lot of lights but will have it soon...now I have the 580 IIex.

this picture shows what I am thinking( bad pic I know ,but with a dirty cheap cell at my office ..)

let me describe this
At each corner(or where need it) a YN flash with a receiver(cactus v5 or RF603/602) the room is huge( well, is ballroom)
Camera with bracket wich will have PW FlexTT5and 580 to camera hot shoe and cactusv5or RF602/603 via PC to camera
The little guy is an assistant with a soft box/pwflexTT5 and any ETTL flash(YN or canon) close to my main subject
The idea is to set the corners lights to lit the room when need it but having PW will help to have good expo over the subject
Let me hear what you think( even if this is a crap ) or if you have a more efficient(cheaper ) way to do this