Chop up the banana and place it in a blender. Cut 2 small wedges from the slice of pineapple and set them aside for your garnish. Cut up the rest of the pineapple slice and add it to the blender. Add the pineapple juice and process until smooth.
Add the ice cream or sorbet, coconut milk and a little of the ice, and process until smooth. Pour into two large cocktail glasses, and pour the grenadine slowly on the top of each drink. It will create a dappled (spotted) effect as it filters down in the glass. Garnish each glass with a wedge of pineapple and a cherry.