[wulf]

Take lots of pictures! It's hard to get everyone together but you can make up for it by trying to capture at least one good shot of each person there.

Also, scope round for good backgrounds. In this shot there is a dark area on the right which might have made a good background for a series of informal shots of smaller groups.

I think you've done a good job getting people in this shot though, especially given the constraints you were under.

Wulf