Sounds like a good plan. Being that your shooting with the 5Dmk2 you can easily adjust your ratios from the rear panel on camera, which is very convenient so you can tweak setting easily on the fly.
How far away will the 430EX be from your 580EXll? Is the room larger with high ceilings? I would only be concerned about the communication of the IR signal. I always found it hit and miss depending on the situation and so I ultimately went with cybersync wireless trippers.
You might want to get your settings to eliminate most ambient lighting and get everything with the strobes, so that you don't run into light temperature conflicts.
Or, put some warming gels over the strobes and let the ambient light blend in, with your white balance setting on Tungsten.
If your light stand will not be in the way, I would go for it.