I think that you've answered your own question based on your parenthetical remarks.
Combining mourning and joy at the same event or day is quite common, actually. In Israel, for example, almost immediately following the joyous Simchat Torah dancing, they recite Yizkor. At one wedding that I attended, they said "Kel Maleh Rachamim" for terrorist victims in Israel, as there was a bus bombing on the day of the wedding. BTW, many wedding invitations include the names of deceased parents & grandparents (I did that on my invitation). So, in a sense, we combine joy and mourning. In your example, after kriyah, the bride and groom can and should change their clothes.
Further support, perhaps...
My wife's friend has been a congregational rabbi in several congregations for many years. He is Orthodox. He has told me numerous times that there are many days where in the morning, he wears a black suit, and goes to a funeral, makes a speech, and cries with the mourners. After 30 minutes, he leaves, goes home, puts on his bright suit, and leads a wedding, with a smile on his face. An hour later, back home, he puts on the black suit, and attends another funeral. OK, he's not doing kriyah, himself. But the point is, that obviously, switching between mourning & joy is possible and quite common.