My idea was to base a party on the old TV Show, Let's Make a Deal. Guest would be given a small item to trade.  Contestant # 1 would come to a room with 3 Appliance boxes. Then they would choose to trade their item for what was behind box #1,2,or 3. Let's say there was a Barbie doll behind box # 1. Then if the person wanted to trade for what was in another box. Then you come and pull the doll's skirt up and there is a pretty ring and in the next box was a plain quarter. Then you would go on to the next Contestant and so on. For invitations, I would make them on the computer and on the front it would say "You've been invited to be on Let's Make a Deal". For decorations I would have a fake audience painting.  This idea would be ideal for 9-12 year olds.