Don't wait around for someone else to throw a 250th birthday party. Have a big cookout for the neighbors. Decorate. Read the Declaration of Independence aloud (you can pass it around, letting each guest read a few lines--don't forget the kids, too). Buy some fireworks and light them off. Play patriotic music--there's plenty on Spotify, Pandora, Apple, etc. Wish people a "Happy 250th."
This is an amazing country, and one thing that has made it amazing is not waiting around for someone else to act.