Combine first 6 ingredients in a large bowl, stirring well. Place half of fruit mixture and half of banana in container of an electric blender; cover and process on low speed until smooth. Transfer pureed mixture to a large bowl. Repeat procedure with remaining fruit mixture and banana.
Cover and chill at least 4 hours or up to 2 days. To serve, stir chilled soup, then ladle into individual bowls. Garnish with mint sprigs, if desired.