Traveling to Japan with children is always a bit stressful: everything is new, the language is different, the pace is fast. It was important for us to have a stable connection. I got a Mobal eSIM
https://www.mobal.com/japan-esims/ , and it really took the stress out of it. We were constantly using maps, checking train schedules, and looking for cafes where we could eat safely with the kids. If anyone got lost in a store or on the subway, we could always quickly call each other. When you're traveling with family, these little things give you a sense of security.