We do a big Halloween bash every year. We do a cardboard box maze through the dark playroom and have a dad stand at the back entrance (which is my back driveway) to scare the kids as they come out. We also do the monster mash, a "cupcake" walk, musical chairs and various other party games.
Kids each bring a dollar store prize and everyone wins the costume contest. As guests arrive I have a parent stationed at the door recording what the costume was, then she makes the winner certificates.
Kids will usually pick what they brought, cause they wanted it or they wouldnt have bought it! lol And everyone getting a prize is so much fun.
This year we are adding a sno-ball fight to kick off a good winter! www.candisno.com
Good luck and have fun!