[ It's fine, he'll probably take responsibility...for at least part of it...? He tries. Attire, though? Hopefully she has something that'll fit the theme, but she's a classy lady, so maybe she has something that'll work- ]

Dress how you would if you were a VIP for a nighttime event.

[ This is not very specific at all. Hm. ]

As in, you know, wear a nice dress or something!

[ This is also not very specific. ]

...Or you can send me a pic of what you've got in mind, and I'll tell you if it'll work.