set up advice needed

I am still not sure about my flash/lighting skills, so I cry for help.

What I have:
3 PWs
1 EX580II, 1 EX430
One 8' light stand with a 43" white and 43" sliver umbrella
one reflector with holder, white/gold/sliver
one 2' backlight stand

Environment:
a medium size of dance practice room, white ceiling (not high ceiling type), background wall can be white or red, room lights at night is bad.

Like to achieve:
some nice single candid shots, buddies and group shots (up to 15ppl) inside the room

There is no time to add any addition gears for the gig. What shall I set up the ones I have to achieve best result? It will be first time for me to use PWs and manual mode on flash. Any practical experience on those setting are welcome too.

Much appreciated...

For candids your best option is flash bounced from the ceiling. The only other option that comes to mind is lighting the room with your flashes, but not sure you have enough lights for that.

How can I light the room or try to light the room?

When I light a wedding reception I put 3-4 flashes pointing at the ceiling in different parts of the room. If it's a high or dark ceiling i'll use direct flash from a couple of directions onto the area of the subject.