Beppu or Yufuin with kids? Choose by your child's age: private-bath ryokan, tatami rooms, big resorts, rooms for 5, free co-sleeping ages and access from Fukuoka.
How to pick a Yufuin ryokan with kids: private family baths, in-room onsen, tatami rooms and in-room dining, plus bath tips by age, rooms for 5 and station access.
Pick an Okinawa babymoon hotel by airport transfer time, in-room bath, in-room dining and late checkout: 6 Okinawa resorts plus 4 Hakone and Beppu onsen stays.