My recommendation is that whenever it's a Sunday / public holiday, we won't visit premises like Kidzania (other examples are museum, aquarium, zoo and amusement park) unless you really want to / you've got no choice, as many children are expected. Better save it on a weekday / non public holiday.
Last time we went to the one in Tokyo. The session was before noon until 4 or 5 pm in the afternoon (timing may be wrong, but it's daytime). Then we walked around the shopping arcade and had dinner nearby. A day full of satisfaction!