I am hereby requesting a leave of absence for one week, from September 3 through September 7, 2007.
This is to facilitate a surgery which my daughter will be undergoing on the September 4, 2007. This is okay, but a bit formal. I would write "My daughter is having surgery on September 4 and I need to assist her before and after the procedure." Or something like that.
This is a bit odd: Your usual cooperation is desperately needed. How about "I would greatly appreciate your granting this request."
(Best wishes for a speedy recover for you daughter, by the way.)