Organizers say the event is open to everyone but geared toward gay students.
The American Humanist Association also will contribute $20,000 for the May 8 event in Tupelo.
The annual prom is organized by the Mississippi Safe Schools Coalition. This year's event has drawn attention because of the case of Constance McMillen, a high school senior who challenged her school district's rule banning same-sex dates at proms.
Coalition spokesman Matthew Sheffield says plans for the event haven't been completed. He says Bass, who is gay, is among the celebrities expected to attend.
