That's a tough one. What kind of job is this for? Sounds like a trick to me. I would avoid being "VERY casual" and go with some kahkis, a nice polo and decent shoes. That way, you look more dressed up than usual but not in a full out suit.
If no one can see them, why not, if it was visible, it might clash a little, but hey, if you have them, use them, no harm in that
If no one can see them, why not, if it was visible, it might clash a little, but hey, if you have them, use them, no harm in that