What are good songs for a wedding?

My dad and his fiance are about to get married this summer and I’m in charge of selecting songs for the whole day. The only song set I’m missing are the songs to be played during the ceremony itself. I was thinking of playing the song my dad’s fiance sang during the first time they met in an international dating social event. But I was thinking of using it for their first dance together. Another option was using the first song they sang together during karaoke night the day she first met our family. What do you guys think? Any suggestions?