I like Audra McDonald, and I wouldn't mind seeing her in the role, but regardless of race she just isn't my top choice to play the role.
Yes, Laura Michelle Kelly would be wonderful but she sounds like too obvious of a choice after MARY POPPINS. Wouldn't she want to stretch those acting muscles a little more? And believe me I know the role of Mary Poppins is very different from the role of Anna, but I rather see her play a completely different role like say Reeno Sweeney in the current production of ANYTHING GOES.
I much prefer the out-of-box casting idea of Lauren Ambrose, but that's just because I think that type of casting often creates the most surprising and exciting turns (see Sutton Foster in ANYTHING GOES, for example).
"Some people can thrive and bloom living life in a living room, that's perfect for some people of one hundred and five. But I at least gotta try, when I think of all the sights that I gotta see, all the places I gotta play, all the things that I gotta be at"