"So Long, Farewell" from SOM is sort of a lullaby, although it's a bit too uptempo.
How about "Tevye's Dream"? Just Kidding!
"Whistle Down the Wind" would work well. I think waltzes are the best, however, because of the swaying tempo - good for rocking a child.
Audrey
Audrey, the Phantom Phanatic, who nonetheless would rather be Jean Valjean, who knew how to make lemonade out of lemons.