My birthday party theme is centered around MODEL ROCKETS.  I provide the opportunity to construct and finish model roctets and then eventually at the end of the party launch the same. Based on the age group the rockets are pre-constructed. For example...if the party was scheduled fot a group of five year olds the rockets would be nearly completed. The kids would only have to paint and/or decal the rocket before launching. If I am working with an older group the students would take more responsibility with attaching the recovery system (the parachute), fins and possible the nose cone.  Each guest at the party keeps their rocket. In addition I take a picture of each child with the finished rocket and enclose it in a birthday card awarded to each quest. Everyone leaves the party with a parting gift with the picture card serving as a form of advertising. I can truly guarantee everyone will have a BLAST!!