That is an ambitious itinerary.

I'd recommend ryokans for occasional 1- or 2-night stays. More will become repetitious and boring. Many hotels offer "Japanese-style" rooms that can accommodate 2 adults plus 2 kids.

You will be visiting during the late monsoon season so be prepared for lots of rain and occasional plan changes due to rains. The later part of your planned stay will be during the hottest, must humid part of the year. Be prepared for it and plan some indoor activities to take advantage of air conditioning. Lots of water and rest stops.