Re: WHAT. Nyx: you know what makes for being super zen on your wedding? Already sort of being married for it. He was relaxed and happy throughout everything, gave a toast to everyone who came during dinner and made sure to find some time to talk to everyone and thank them (and hugs if they're huggers!) during the night.
Gladio: will hit up the dance floor, is generally just enjoying the night and having some drinks, eating food, probably being super obvious every time he glances at Noct. The usual. Will chat with whoever so if anyone wants to assume some vaguely buzzed conversation on the merits of things people discuss after a few drinks please do!
Natasha: is very happy to see her dear friend get married. Is not a speech person but will talk to them during the night sometime and give a little one between the three of them. Will be drinking and dancing, will at some point lose the heels because she likes not destroying her feet.