An ice cube tray works well for freezing the pumpkin in pieces.
Using a high speed blender, place in frozen banana and pumpkin, and crush until all chunks are gone. Add other ingredients and blend until smooth. You may need to use a spatula to scrape down the sides of the blender cup a few times to get all of the ingredients properly mixed. It will be like a soft serve, but if you like your ice cream firm, place the finished product in a bowl, and set in freezer stirring occasionally every half hour until desired firmness has been achieved.