Smaller one... Simple PVC sprinkler that the kids can ride through on their bikes! My boys would love this and even the youngest on the trike could join in! Nice instructions here- click the thumbnail for step one :)
PVC Sprinkler Water Toy - how smart is this? $10 worth of materials from the hardware store will bring lots of joy this summer. :) My friend did this with her kids and used a couple of pipes and plastic streamers as well, they called it a "car wash" and rode their bikes through it. They played with it all summer.