Re: WHO.
Steve's for sure there, of course, and did not forget the rings. He'll be in whatever appropriate groomsman suit is determined lol (are they all supposed to match? does he need to run things by a wedding coordinator? are there rules?)
Brigitte would be there, hanging with the Asgardians if they'll have her - she's kind of an honorary Asgardian right
Kratos will actually show up, y'all, but don't expect a suit. He's there to support his allies and wish them a good future. He's not sensitive, shut up.