Eli Salazar
Eli was there as a groomsman! Mikhail was one of his first friends coming to Dunhaven, courtesy of Annie, on top of their fun and complex dreaming connections, so he was pretty happy to be asked to be one. He's kind of a sucker for weddings, especially when they're for people he particularly cares about.
When he wasn't needed for groomsman duties, he would have been pretty focused on Caty (I'm assuming she came despite being super pregs, but correct me if I'm wrong, Kit!). He did probably dance a bit with a few people, like Annie, Emilia, or Angie, but otherwise would have been laser focused on his girlfriend. I don't think he would have drank much outside of maybe some wine with dinner, so he was his generally mellow self!