Well, my 5YO will dress as an astronaut for his school party. My 20MO will be Scooby Doo. We'll take the kids around the neighborhood to trick or treat. The neighborhood is only about 20 houses, so it's just the right size.
One of our neighbors throws an annual Halloween party for adults, so we'll go to that. Our costumes are TBD.
We do need to decorate the house. DS noticed other houses with some cool decorations and wanted to know if we'd be decorating this year. One more thing to do... At least it's a fun thing, right? :)