Wonderful Tonight is really cute. It's my parent's wedding song.

I really like this list of First Dance songs on OBB, though I'm sure you saw them.

Of that list I would say...

* Definitely put the Mario Kart Love Song if your sister is a dorkling.
* Nancy Sinatra's "Sugar Town" (Alternatively: Zooey Deschanel's cover)
* The Cure's "Friday I'm in Love"
* The Cure's "Just Like Heaven" (honestly, I'd also add Love Song to the mix!)
* She & Him's "I Was Made For You" (This is really dancy and cute!)
* Edward Sharpe & The Magnetic Zeroes - Home (this song is fun and romantic, has a bit of a country twang to it. I could see people dancing and bopping to this)

PS: This song would probably be my wedding song, or maybe Sugar Town. I love both songs.