Backyard fun: 10 Creative Ideas to Make an Outdoor Oasis for Kids this Summer Apartment Therapy
Wooden Playground Monkey Bars - would make a great ladder to the tree house!
An amazing sandbox for the kids.Playground Build & Design Natural Child Play Earth Wrights Ltd
Cool idea for backyard obstacle course.
8 Easy and Affordable Kid-Friendly Backyard Ideas - thegoodstuff
"Textured Painting - Natures Paint Brushes" This is not just art, but art in nature! Go on a nature walk to gather 'schtuff!' Then use what you gather to create art or As art!