In a large bowl, combine the first 9 ingredients. In another bowl, combine the eggs, pumpkin, bananas, buttermilk, oil and vanilla. Stir into dry ingredients just until moistened.
Coat muffin cups with cooking spray; fill three-fourths full with batter. Bake at 400° for 15-18 minutes or until a toothpick inserted in muffin comes out clean. Cool for 5 minutes before removing from pans to wire racks. Serve warm.