There’s a lot of nice places to walk around in Odaiba. Weekends and holidays get very crowded though. The kids love to play at the little beach which is near Aqua City. No swimming is allowed but they enjoy playing in the sand, while us mommies sit on the boardwalk with the babies. Right across the street there is a puppy rental shop. We’ve never tried it though so I don’t know any of those details. Kids might enjoy taking a puppy for a walk along the beach. It might also be a good idea for kids who want a dog to see what it is like to care for one for a day. After sand time (and washing off) it’s an easy stroll to 
Decks, where they have little Hong Kong and a replica of an old Japanese town which many people find “natsukashi” or reminiscent. Next door is Aqua City, where there is Toys R Us, kids clothing shops, the cinemas. 
The outdoor walkway along Decks, Joypolis and Aqua City leads straight to Palette Town and Venus Fort area. There they have the Toyota Showroom where you can drive cars along a track, the huge ferris wheel, a big game center, and of course more shops and restaurants.
There are milk rooms all over in Aqua City, and Palette Town but I like the one inside the Toyota Design Center because it doesn’t get as crowded and there is a small play area right in front of the milk room.