Cut the top and skin off of the pineapple and cut in to chunks. Peel the banana and break in to pieces in the blender. Add the pineapple chunks, coconut milk and yogurt, and process until smooth. (Add a little water if the consistency is too thick.)
Pour the mixture into 4 glasses.
Note: The coconut milk adds plant fats that help support the immune system, and your child will burn them off as energy instead of storing them as fat.