If it were now I would probably choose City Of Blinding Lights. Just the chorus of ‘Oh you look so beautiful tonight!’ can be meant for your guests, bridal party and more importantly your bride!
There are piano/string versions of U2 songs online that I used for my wedding. I don’t know how you’re wedding is going to be, but if you’re talking about walking down the aisle, I would say something light like piano/strings. If you’re talking about walking into the reception, then go big with Elevation, Real Thing (Fish Out Of Water), etc.