This might sound silly, but for the seating cards, can you just do first names with the first initial of people for those with the same names?
I'm still waiting on final names from people bringing guests, but my fiance hasn't been getting last names.
(Honestly, I don't really care, but are we breaking some kind of etiquette no-no here if we don't do last names? It turns out I offended people by addressing invitations to [First Name] [Last Name] rather than Mr and Mrs [Man First] [Man Last])
If I should be using last names, is it bad if we have some of the guests with just the first name?