I've done "I Won't Grow Up" from Peter Pan with some of my voice students. It's very cute.
"First up was Max who sang "Can You Feel the Love Tonight?" [...] I haven't seen that big of a reaction to a stair descent since Audra left the attic in Ragtime." --Seth Rudetsky
I love "The Graveyard" from JANE EYRE. It's not a clearly defined song that might work well for you, but it's one of the most beautiful duets (there's a duet in the middle).