Have a red, white, and blue taste test with the kids. Put out all sorts of foods and spices in a series of small dishes. Blindfold the kids and have the kids taste the foods and spices and guess what they are. Ideas for tasting include salt, ketchup, blueberries, strawberries, French salad dressing, mayonnaise, sponge cake, strawberry jam, pepper jack cheese, beets, tomatoes, garlic, bananas, cherries, etc.
Freeze blueberries and raspberries in ice cube trays to make star spangled cubes.
Make a rocket pop drink. Fill a glass with ice cubes. Carefully pour cranberry juice, blue Gatorade, and 7-Up into the glass directly over the ice cubes to maintain the patriotic colors.
Using blackberries, cut up/halved strawberries, and bananas, have the kids create a fruit flag using the fruit pieces. They can place this on a cookie tray, and then you can lay it out to serve to the rest of the guests. The kids can also make mini flags for themselves. You can also provide lollipop sticks to the kids to skewer the fruits with.
Using a star cookie cutter, make up a batch of patriotic gelatin stars, star sugar cookies, cheese slices, and sandwiches filled with cream cheese and blackberry jam.
Make a batch of cupcakes and have the kids frost them and decorate them with red, white, and blue sprinkles.