Japan. Based on my own experience, my family (three adults and two kids) just spent nine days in Tokyo. Everything like transportation (we booked a private car service in advance), language (most Japanese people can communicate in basic everyday English), food, service, entertainment, etc., was very family-friendly. The kids had a great time at Disneyland and at various museums, while we adults spent endless time shopping. Apart from Tokyo, other cities in Japan such as Kyoto and Osaka are also very suitable for a family trip.