Play Landscaping - Infinite Playgrounds this would be cool for the little kids to crawl into!
Use flagging tape (similar to caution or police tape) in colors and patterns to hang from trees at a party or playground.
Water wall made with bamboo guttering attached to fence
Rather you can incorporate elements of child-friendly design into your own small space.
outdoor music station 1 Wonderful DIY Outdoor Music Wall / Station For Kids
'Gongs' built into a fence - (kids, backyard, playground, play space, fun)
Natural Playgrounds Company built a slide into a constructed hill at an elementary school as shown here in Glens Falls, N. The embankment slide is safer than tower slides with ladders. Scattered boulders, random dirt steps, rough terrain and varied plan
Simple playhouse from the February 2016 issue of Inside Out magazine.