The cool thing about this scenario, is that the kids came up with the trap idea by themselves and they worked together to make it and set it. I tossed in the bit about having to go to sleep-they don't naturally go to sleep very well on their own. And they did all fall asleep!! I took out all their green toys and left them some gold coins (that look suspiciously like pennies) and some green pixi sticks. I also left them a note from the Leprechaun thanking them for the house, but telling them that he was headed back to Ireland.
Happy St. Patrick's Day!