The event is to take place Jan. 7 at the Beverly Hilton Hotel.
Confirmed to attend are Jon Hamm, Elisabeth Moss, Jared Harris, John Slattery, Mila Kunis, Julie Bowen, Jesse Tyler Ferguson, Marcia Cross, Rashida Jones, Jennifer Westfeldt, Amanda Seyfried, Cindy Crawford, William Shatner, Cybill Shepherd, Jaime Pressly, Jason Bateman, Vanessa Williams, Hilary Duff, Daisy Fuentes, Harry Hamlin, Lisa Rinna, Alison Sweeney, Amber Valletta and Diahann Carroll.
Bennett was a personal friend of St. Jude's founder, the late entertainer Danny Thomas. He will perform for the star-studded crowd along with Romano, a friend of the Thomas family and a supporter of St. Jude, to commemorate what would have been Thomas' 100th birthday. The 50th anniversary gala will also honor St. Jude's commitment to saving the lives of children fighting cancer and other deadly diseases, organizers said.
"My father always said there would be no St. Jude without Hollywood," Tony Thomas, son of Danny Thomas and one of the gala's co-chairs, said in a statement Tuesday. "He spent the 1950s raising money for his dream, to build a hospital for research and care under one roof for children with cancer and other catastrophic diseases. He reached out to his entertainment friends, who we now know as legends, to put on benefits around the country to raise money for a hospital yet to be built. Today, St. Jude Children's Research Hospital stands as a beacon of hope for families across America. My father would be so proud that Hollywood continues to support the hospital."
"Danny Thomas was an exceptionally generous man and I loved having had the opportunity to know him," Bennett said. "He passed along his giving spirit to his family and I know he would be so proud that his mission to help children through St. Jude Children's Research Hospital has continued on so successfully. I am thrilled to be part of the 50th anniversary to celebrate this wonderful organization and honor Danny."