I'm invited to a surprise birthday party for one of my supervisors at work. The party is Saturday night at 5:30 at the guy's home. The invite has no indication regarding appropriate dress and I don't know his wife/party hostess, so I don't feel comfortable calling to ask.
We generally dress in suits at work or dressy business casual, but I have no clue what to wear. Only one other person from work is invited to the party and she is equally confused about what to wear.