Decorations: Anything red, white, & blue. Be sure to include stars, flags, and fireworks.
Food: Hamburgers, hotdogs, watermelon, corn on the cob, & blue raspberry punch.
Games: Fireworks are always a great idea (especially the ones on TV)
Reach For The Stars - You'll need star shaped sugar cookies, string and blindfolds for this game. Hang the red, white, & blue decorated star cookies from a tree branch, clothes line or ceiling. Everyone stands in front of a cookie blindfolded. The first one to eat his/her cookie without using his/her hands wins.
Rocket Balloons - You will need red & blue balloons, streamer ribbons, & dried lentils. To make each rocket, use a kitchen funnel to pour 1/3 cup of dried lentils into a round balloon. Then blow up the balloon so it's about 16 inches around and knot it. For the finishing touch, tie several long ribbon streamers around the neck. Toss back and forth. See who's rocket can go the farthest.
Patriotic Parade - ask guests to bring wagons, bikes, scooters, drums and tambourines. If you don't have any of that decorate poster float. Use balloons, construction paper, streamers, small flags, etc. for decorating the parade floats. Parade around block or a park.
Wizarding Duel - use sparklers as magic wands to have a family wizarding duel. The wooden sparklers with the long handles are the safest. Give out awards for style, speed, sneakiness, etc...