Also on these boards
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 :)
water play with multiple activities. It would be neat to have an area where several short hoses and sprayers with containers could be attached. I'd make it longer so that children would be spaced farther apart but I like the natural look of what appears to be a wooden wall and possible wooden steps or a bench behind it to provide better access from the top.
Water tables are really neat, but expensive! Use a small plastic pool, set on milk crates-doing this!!!