Seven young actors have been cast as the von Trapp children in the musical production of "The Sound of Music Live!," U.S. network NBC announced. Playing the singing youngsters in the holiday program will be Ariane Rinehart as Liesl, Michael Nigro as Fredrich, Ella Watts-Gorman as Louisa, Joe West as Kurt, Sophia Caruso as Brigitta, Grace Rundhaug as Marta and Peyton Ella as Gretl. Starring country music artist Carrie Underwood as Maria and "True Blood" actor Stephen Moyer as Capt. Georg von Trapp, the 3-hour telecast is to air Dec. 5. The cast will also include Broadway titans Audra McDonald as Mother Abbess, Laura Benanti as Elsa Schrader and Christian Borle as Max Dettweiler.