You could make shandies. Half beer and half lemonade, http://en.wikipedia.org/wiki/Shandy.
As for potato salad, using white wine vinegar can give it some flavor and keep it light without mayo.
You could make popsicles for dessert--get some yummy juices, like mango or whatever and freeze it popsicle makers.
And my favorite ever recipes for peanut butter pie (it makes two!):
1 cup powdered sugar
1 (8-ounce) block light cream cheese, softened
1 cup natural-style, reduced-fat creamy peanut butter (such as Smucker's)
1 (14-ounce) can fat-free sweetened condensed milk
1 12-ounce tub frozen fat-free whipped topping, thawed
2 9-inch ready-made reduced-fat graham cracker shells
4 teaspoons fat-free chocolate sundae syrup (if you want it)
Combine the first 3 ingredients in a large bowl; beat with a mixer at medium speed until smooth. Add the condensed milk, and beat until combined. Stir in the whipped topping. Divide the mixture evenly between shells; put in freezer 8 hours or until set. Cut into wedges, and drizzle with chocolate syrup, if you want.