re: Cocktail attire question

Dillards, but the Mall of Louisiana store, not the Cortana one.
I'd wear a suit to a wedding, better to be slightly overdressed.
By the way, I attended a pretty damned nice party two weekends ago, and opted out of seersucker, because it was at night. It was hot as hell that evening, and dontcha know five or six old bastards wore seersucker that night. I coulda kicked myself for not wearing mine. I'd have been much more comfortable.