1/2 cup 100% coconut water (rather than coconut milk)
1/2 cup watermelon
4-5 frozen strawberries
Mix all the ingredients with an immersion blender (or any other kind of blender).
This could easily be doubled/tripled etc for more people. Adding in ice would add to the icee like feel of this drink and make it even colder.
For more calories (if you have a little on who needs extra calories like mine were) you could use some coconut milk. Maybe 1/4 cup. Let me know what variations you come up with.
This is so simple that children can very easily help to add ingredients in. Help with measuring and pushing buttons on a blender. Little cooks in training and learning math through cooking! Woo-who!