There are some really cool outdoor playgrounds in Tokyo.
One of which is Koganei Park (close to Musaashi-sakai ), the second largest park in Tokyo, which has a really decent sized adventure playground, complete with flying fox and supervised inflatable bouncing mountain.
On Sundays in summer the park plays host to the local flea market which is stacked with secondhand brick a brack and goodies. Perfect if you don't mind buying used designer label clothing for your young children.
The park also boasts a large area dedicated to the history of Japanese architecture. With many old Japanese buildings and gardens dating back through time this architectural museum is fun for kids and adults of all ages.
You can BBQ in the park too with a well established area just for this purpose, and if you have a dog there are a variety of dog runs for big and little pooches.
Wide open spaces make this park great for kite flying and ball games, and the secluded forest and pond areas make it a shelter and natural habitat for beautiful blue king fishers and mountain birds. Just the laid back vibe here makes it well worth the visit.
This Park is particularly beautiful in the autumn, delightfully green in summer, and is very famous for the best cherry blossom viewing in Tokyo.