Nikon D3100 Portraits and body shots?

What would be the best settings for a Nikon D3100 to take great photos of a few girls of head shots and body shots and group shots of them together. They are planning on having me take some with them and umbrellas, and colored stringed holiday lights, etc.

Assuming you have the 18-55mm kit lens, zoom it to about 50mm and step back from the girls for head and body shots. Same distance, but you can zoom out for group shots.

If you are not happy with the Auto mode, Portrait scene, try the Aperture priority setting of as open as you can, such as f/5.6.