Surprised dance with choreography

I would suggest reaching out to your local dance studio (even if the only local place you have is one of those places that teach dance to young girls). See if one of the dance instructors can help choreograph something for you, and spend a few nights teaching you the routine. They will have lots of options/suggestions for songs.
Or, if that’s not a possibility, you could look on YouTube. There are lots of instructional dance videos there. Maybe you could find one with music you enjoy

Just as a slight word of caution, is this something you're planning to pull focus for a whole song? Or is it more something you guys can do while everyone's dancing? If you're planning on a sort of solo performance for a whole song, that can get old fast, and the song will seem like it goes on forever. Unless you both are unusually good dancers, it may come across as a bit amateurish, but of course you know your crowd best. I would suggest doing a routine during times where everyone is dancing or limiting the solo time to around a minute.

I’d caution you that performances of this kind at a wedding are divisive and not everyone’s cup of tea. It’s certainly not something I’d ever advise you do as a surprise. Keep in mind too that your guests are a captive audience and some will find these kind of things attention seeking or inappropriate to the time and place.

Are these expected in your culture? Surprise events of any kind that the couple themselves don’t plan themselves rarely received well. Guests don’t enjoy watching them either and feel they are inappropriate for the event.

Do you have a song in mind, or would you like ideas?