This is such a good idea. And what a fantastic way to hang on to the last few weeks of summer with glasses filled to the brim with some Frozen Watermelon Lemonade. What I love about this recipe is that you have so many ways of serving it. Keep it as a slushy of the mixed watermelon and lemonade or top it up with soda water for more of a cool drink. Make it festive and top up half a glass of the mix with some bubbly or go the cocktail route and top it up with rum, tequila or vodka. The options are really endless.