Branwen,
You said they're friends of yours. Did they invite you to audition? If they've already expressed an interest in you, it's entirely appropriate for you to just ask them what they want you to do in the audition.
Remember, too, that they want you to be good. Listening to bad auditions is excrutiating, and they'll be delighted if they have too many good choices to consider.

A couple of years ago, I was asked to audition for a show, and the director asked me to sing a particular song. I prepared another one as well, not realizing that the real point of the audition was for the music director to hear me, because the director already knew exacly what he wanted me for. When they tell you what to do for the audition, pay attention. It saves lots of trouble.

Dress comfortably, and in what you know flatters you. If they're looking for women, you may as well use your substantial womanly charms.

Let me know how it works out. If you don't, I'll have to ask you.

Mimosa