September 23 is Autumn Equinox Day, a national holiday. What to do with your family? If you have kid, take them out to National Children’s Castle (Kodomo no Shiro). They will have an event called Sports Onigokko, which I believe is basically a hide-and-seek or tag game.
Even if you don’t participate in the event, there are many things for the family, such as a pool, family lounge, etc. Located between Omotesando and Shibuya, it is easily accessible by train. There is even parking space for those coming by car. So enjoy a day out with the family!
Location: B2F of National Children’s Castle (Kodomo no Shiro)
When: Sept 23 (Tuesday) Event is 14:00/16:00 but facilities open 10:00-17:30
Entrance Cost: 400yen/person (Age 3-18) / 500yen/adults