If you had two close seniors or friends that you referred to by last name got married how would you address them? Would you refer to one as their given name, call them both by the shared last name, or something else?
IMO, starting to use his/her given name suddenly is usually an inconsiderate option. (It's fine during their wedding ceremony, though.) You can just use 奥さん or 旦那さん if you are in front of them. In uncommon cases where you need to refer to one of them as a third person specifying the family name, you can say 山田家の奥さん(の方) or something like this. In business settings, you can also use their full names and titles (e.g., 山田太郎先生 and 山田花子先生) when this is necessary to disambiguate.
That said, from my experience, in many cases I had been using given names, nicknames or handles before they married, so I was able to simply keep using them.