What to sing?

Today I have an impromptu audition of sorts.  A friend suggested I sing for an organist, with whom he is also friends, and arranged a meeting between us.  It's my hope a recital or concert series could come of our meet-up.  I've been preparing a variety of selections for the last week and now I find I'm second-guessing myself.  Do I start with anonymously-composed early music that I'm interested in at the moment?  Or a mid-20th Century opera aria that I know well?  Mozart's always nice, and it can showcase coloratura and range, so that might be good.  I could toss some Bach in my bag...

I've got a couple of hours in which to make a choice.  Deciding what to sing can be as challenging as selecting what to wear.