Garnish glasses with additional watermelon cubes and mint.
Double or triple this recipe for a family picnic or party.
As an option when serving adults, prepare drink as directed. For single servings, pour drink into glasses as directed. Add 3 Tbsp. (1-1/2 oz.) white rum to drink in each glass; stir. Or for 4 servings, add 3/4 cup white rum to watermelon mixture with the club soda. Continue as directed.