14-d itinerary N+S Kyushu, JR pass

Hello,

Planning 14-night Kyushu trip for late March / early April. My wife and I, and our 2 kids (3.5 + 6 yo). Appreciate help reviewing our schedule.

Day 1 - arrive Fukuoka airport 1:30p. activate 5-day JR pass (all Kyushu). Take shinkansen to Kagoshima. Stay 4 nights.
Day 2-4 - Ibusuki, Chiran, Sakurajima, (Kirishima? +/- rental car?)
Day 5 - use JR pass to take trains to Kumamoto (Hayato no Kaze, Yoshimatsu, SL Hitoyoshi). Stay 2 nights Kumamoto.
Day 6 - Kumamoto (all day)(castle, Suizen-ji koen, Daikanbo?, Kurosawa onsen?)
Day 7 - Ocean Arrow / Kumamoto ferry in AM to Shimabura (30 min). Rent car. Drive to Unzen, Isakaya, Omura. Stay 2 nights Nagasaki.
Day 8 - Nagasaki (all day)
Day 9 - drive Nagasaki to Aso / Kurokawa. Stay 2 nights.
Day 10 - Takachiho in AM. Aso in PM.
Day 11 - Return rental car in AM. activate 5-day JR pass (North Kyushu). Aso Boy (10:05a) to Beppu/Oita. Stay 1 night.
Day 12 - train to Fukuoka / Hakata. Stay 3 nights Hakata.
Day 13-14 Hakata (full days)
Day 15 - train to airport. Fly out

How hard is it to rent car in Shimabura? Planning to return in Aso.

Any suggestions or modifications? Not sure for Aso / Kurokawa / Beppu / Yufuin area where best to base ourselves - to experience onsen and be closely located to the sights. Beppu seems to have more points-of-interest but Yufuin is an onsen town?

Appreciate any insights and advice. Thank you in advance.

The Nagasaki piece seems to be strangely placed. Nagasaki to Kurokawa onsen or Aso or Takachiho is really far. That region is much better reachable from Kumamoto; but even from Kumamoto not really as daytrips (unless you want to be many hours in the car).

So I would do Kagoshima -Nagasaki - Kumamoto and the in to Aso, Takachiho and Kurokawa onsen. I think in that region youfll need to change hotels. Eg Kumamoto, Takachiho and Kurokawa onsen. And youfll need a car. From Kurokawa you can then continue to Beppu.

In Northern Kyushu have you heard about the toilet museum? I havenft been but sounds like fun, specially with kids.
https://www.japan-guide.com/e/e4883.html

Enjoy your trip to Kyushu!