Could you dig up a small patch of "real estate" in that front yard cemetery and bury a little locked coffin with the prize inside? You could even add a small scavenger hunt aspect... gotta make 'em work to find the shovel, right? Kinda reminds me of the end of the Addams Family movie where they all merrily went out to dig up the relatives... heh
One year I attached a big spider to some dental floss, used some eyelet screws and ran the floss from the spider to the door. When the door opens the spider drops. Got a lot of fun out of that one.