Process half of lemonade, half of limeade, 1/2 cup powdered sugar and 3 cups of crushed ice in blender. Pour into a 4 liter jug. Repeat with remaining ingredients and pour that into the jug too. Place into a freezer until mixture becomes firm.
Remove from freezer 30 minutes before serving. Rub rims of glasses with lime wedges; place salt in flat bowl and dip glass rims into salt. Add club soda to the lemon/lime mixture, stirring until it becomes slushy. Pour into prepared glasses.
You can make this a regular Margarita by adding a cup of tequila before freezing.