My own personal favorite lullabyes -- and it's been quite some time since I had occasion to use 'em -- were "Kumbaya" and "Buckeye Jim." The latter is in the DT (with slightly different words), but my dinosaur computer system won't support audio, so I can't tell if the tune given is the beautiful one I know, which would be great for harmony. The DT gives no source for the song, and I certainly have no idea where it came from -- might very well be public domain.
Your CD project sounds terrific. Be sure to let us know when it's available!