Lemonade and Orange Spritzers

1 (12-oz.) can frozen lemonade concentrate, thawed
1 (12-oz.) can frozen orange juice concentrate, thawed
1 cup water
2 (1-liter) bottles (4 1/4 cups) lemon-lime flavored carbonated beverage, chilled

In 4-quart nonmetal pitcher or bowl, combine concentrates and water; mix well. Add carbonated beverage; mix well. Serve immediately. If desired, garnish with lemon and orange slices. Makes 12 (1-cup) servings