how to light up a party shot/portrait..

How would I go about doing a portrait outside in a party setting? Basically, in the frame, it'll be a small party with a group of people but emphasis on one single person. Probably about 12 extras. The extras will be standing around and so will the main subject but main subject will be the only person looking at the camera. How should I approach the lighting? I guess this is a little more complicated than your typical how do I light up grandma for the Christmas card but any help is appreciated thanks! I currently use hot shoe flashes with 60" reversable umbrellas, this may or may not be enough..I may have access to proper monolights

I'd probably put a light on the main subject, off to one side, maybe with fill. Put another light or two on the others, again not from the direction of the camera, but with fill if needed. Gels might be nice too. I'd say you can do this without monolights, 2-4 hot shoe flashes off the hot shoe as lights on the people would be enough, and maybe maybe a light or two on the background if it's too dark.

I can't find the image, so I'll have to describe it.

I've seen it on a lecture series on TV maybe 3 weeks ago. A woman photojournalist with a photography degree from oxford decided to visually document the social pressures influencing behaviour of girls... little kids. There was lots of talk about peer pressure, advertising, obesity, anorexia, bulemia, depression, sexual development, conformity... blah blah blah...

She had to do a shoot for some reason related to the whole thing and she chose Tyra Banks because her measurements are closer to "normal" women and further from a typical model.

And there's this shot of banks on the beach. I thought it was fascinating it was so simple:
Banks in the foreground
About 6 guys in the background "observing" the shoot (as it seems from the photograph)
The sun is behind them
It's a "sunny 16 exposure"
Banks' face is lit up by on camera flash
The guys are just silhouettes. You don't see their faces.