Hah, we belong to the same club. This kind of stuff stresses me out too.
I guess, I think the question of coat is dictated by climate. The cotton trench could work for a spring evening, but will it be warm enough for a winter event?
I imagine you’ve checked out J Crew’s offerings for colorful wool coats? They seem to still be the go-to.
Also, once you’re inside and take the coat off, will you feel too plain? Do you need an extra dose of color/pattern/texture somewhere in the outfit? I know you were pondering a pashmina at one point...
Those pom pom earrings are super adorable. Oh -- and have you looked at Madewell for tassel earrings? They have a bunch of different colours right now. I didn’t check the dimensions, but they don’t look too long.