Dressing a Room vs Dressing Me

My husband and I are invited to a "black tie optional" event being held in January.  If it were a "black tie" event, I'd know exactly what to wear.  The "optional" is what is throwing me off.  If a client asks me to create a formal living space for them, I know what formal pieces of furniture will work and I'll use a symmetrical arrangement.  For a casual living space I would place the furniture more randomly and I'd use soft, comfy fabrics.  Whatever they want, whatever style, level of comfort I'm sure I could satisfy their needs.

I'm also very confident in choosing clothing and how I dress....usually.  It's not often that I attend a formal event.  And styles and customs change from time to time and from one region to another.  So, I'm finding myself in a quandary.  I googled "black tie optional" and then went looking for a dress.  Imagine how happy I was to find something on my first outing.  I bought a nice evening bag and am looking for shoes.  Also, I went through my jewelry box and found the perfect jewels. 

I should have stopped there.  One last "google" to make sure everything was ready.  It seems like every site says basically the same thing, then each one adds a few extra comments to confuse the issue!  Now, I'm having second thoughts on my choice, time is running out, and since many women are now shopping for New Year's Eve dresses, I think my choices will be very slim. 

Probably all will go well, although at the moment, I'm a little stressed.