Need some advice here. A friend asked me to do a costume shoot for her dance group, basically the costumes of the their upcoming performance.. it's gonna be done in a dance studio and i'm ill-equipped in terms of lighting equipment. It's gonna be experimental, I'm new to this and i'm not charging them.

I currently have a 580ex mkI. I'm thinking of renting a ST-E3, another 580. So that i can have up to 2 off camera flashes.. i would probably need 1-2 silver brollies to soften the light?