Honshiba Park.
It is 8 minutes from Shinagawa Station by cab (approx 1200 yen)or 33 minutes on foot. You could also take the subway for a 5 minute trip to Mita Station from Shinagawa, although you will need to transfer once (and at this time I’m unable to confirm if there are elevators for strollers etc.)
It is 12 mins from Roppongi by cab (approx 1300 yen)
It’s a little, thin, long park with a play area, a great view of the train tracks and a water splash area in Summer. There is quite a bit of shade around the pool and lots of preschools and pedestrians near by – giving it a lovely, safe, family-friendly feel.
There are restrooms and a change table. My little boy loves it because he can see the trains, monorails and bullet trains – all from the same spot. If you wanted to know about other transport related parks that we have found you may like this post on parks for kids who love transport and vehicles too.
HONSHIBA PARK
港区芝4-15-1
4-15-1 SHIBA, MINATO