Actually, I do a lot of wedding cakes and there are a lot of good songs for this. I think Boyz 2 Men has a song called "For my Mother" or some such thing. It's really a lovely song.
I was at a wedding once where the Bride & her Dad danced to Bob Seeger's "Like a Rock". Seems like an unusual selection, I know, but the DJ told everyone to "listen carefully to the lyrics" and it really was a perfect choice. If I could remember the lyrics I'd tell you, but you can go online and get them.
There's also a lot of good songs from Broadway musicals, and don't forget to check out country music lyrics. You'll find something, and it will be just PERFECT. Congratulations!