Mr. Blue Sky - ELO: not about romance, but it’s happy and shiny and fun to bounce to.
Sugar Sugar - The Archies: if you cannot groove to this, you have no soul.
Accidentally in Love - Counting Crows: fabulous song for a wedding.
Congratulations! 
It’s Raining Men
Chocolate Rain?
OK, for serious now.
Queen - Don’t Stop Me Now
Tonight I’m gonna have myself a real good time
I feel alive and the world it’s turning inside out, yeah
I’m floating around in ecstasy
So don’t stop me now don’t stop me
'Cause I’m having a good time, having a good time
It’s insanely upbeat after the intro. Plus it’s about a gazillion times better than those songs they’ve used in the past.
Am I the only person who thinks maybe the fiancé isn’t going to like anything they do? Pick a song he already dislikes, rather than ruining a song he likes with this twaddle.
That said, I think “Love Shack” might work.
All Night Long - Lionel Ritchie
Puttin’ On The Ritz - Taco
Jump - Pointer Sisters
Crazy Little Thing Called Love - Queen
Higher And Higher (Your Love Keeps Lifting Me) — Bette Midler