Dylan's Jimmy: Being the officiant, Jimmy was, of course, there. He managed to make it through the whole ceremony without crying, but broke down in happy tears immediately thereafter. He'd later tell Darcy that he "liked this season a lot better."
Harry: Being Coven buddies with Wanda, was also there, and though formal wear for someone the size of an NBA player was a bit too much for the last minute, did manage to make himself look presentable.
Rhodey: Also there and actually sharply dressed (though he might complain--mostly jokingly--about his mobility harness clashing with the tux). He also called in a favor to get a bottle of Sokovian wine for the newlyweds.
J'onn: Would attend, along with Kara.
Hank, Peter Quill, Mobius, not knowing the happy couple especially well, likely did not attend.
Cliff: Having missed his own daughter's wedding to end up here, definitely did not go, and volunteered for portal duty.