Have several events such as: discus(Frisbee) throw, sack race, tug of war, egg on a spoon etc. Award medals for the events. {Craft store or hand made} Have one event like and obstacle course where each child gets a medal. Events don't have to be physical. You could have silly face contests etc. DECORATE with red white and blue. Use the Olympic ring symbol on the cake. Serve hotdogs if you want. It is really not hard to make sure all kids are winners.