You want to shoot from the floor I presume?
Ceiling height about 2o-25ft??
First thing first.
Camera on Manual exposure, using your fastest lens (50 1.8), shutter speed @1/250 (sync speed for your camera). Adjust your ISO to provide you with an underexposed (say by 1 to 1 1/2 stops) ambient light with your aperture at say F2. Hopefully, depending upon conditions, you will be at say ISO1600, F2 @ 1/250th or there about's.
Flash on camera, set it to standard ETTL, bounced off the ceiling, pointing slightly forward with bounce card extended. I would also recommend that you make yourself a "better bounce card"
The 580EX is a great flash (is it version 1 or 2?)
Irrespective, buy some decent batteries. I strongly recommend Sanyo Eneloop's and a proper conditioner/charger. DO NOT use the fast 15 minute chargers.