OCF placement for indoor baby shower

hey everyone, i've been talked into doing some probono work; my coworker's baby shower in Jan 2010. this is going to be at someones house, i don't know the lighting conditions, arragnement, or size of the room but i would like to set up some off camera lighting throughout the room. my current lighting gear includes 1x 580ex II, 1x 430ex II and a PW for each flash, 2x lightstands w/ 32" umbrellas. where should be the best placement for what i have?

i imagine people will be walking around, socializing, etc.., and so i would like my two light sources to provide enough lighting no matter where in the room i am taking pictures, is this possible? i was thinking about getting 1 or 2 alienbees to replace the two off camera flashes and put the 580 on camera and bounce off the ceiling/wall., but if i go that route, i'll have to switch between the on camera flash and PW. i figure if i bounce the flash it'll allow me to be more mobile whereas, if i setup only off camera flashes, i'll have a combination of dropoffs and hotspots.

any advice is much appreciated. thanks

AlienBees would be way too big and intrusive in someones house, so would an umbrella. I'm not sure you need any lighting at all, but you'll know once you get there.

If you do, put a Speedlite in each corner, pointed towards the ceiling. That will help cover the whole room. You may even be able to use wireless ETTL inside, which would make things easier than manual with PWs.

thanks Tim, so i would use my 580 on camera and triggering my 430ex via IR? i was thinking the exact same thing about bouncing the two flashes directly off the ceiling, but if the ceiling is too high it'll eat my batteries. but i have plenty of batteries so it should be ok.

Yeah, exactly. Use higher ISOs if you want to use less batteries, but you'll have to balance it with ambient/outside lighting.

If it's during the day then you probably won't need flash. Ceiling bouncing flash in a small room often causes worse lighting (especially in the eyes) if you don't balance it well with the ambient lighting, like Tim said. Honestly, I would go in with the plan of shooting available light and have a flash setup as the backup plan if there isn't enough light.