Kyushu Dec Self-Drive Itinerary

Hi, my family and relatives are planning a self-drive trip in kyushu from 12-17Dec. We haven't completed our itinerary yet, but I was wondering if the following is feasible..

12 Dec: Fukuoka - Beppu - Takachiho
13 Dec: Takachiho - Miyazaki - Sakurajima - ibusuki (via ferry to kagoshima)
14 Dec: Ibusuki (haven't decided on the day trip yet. Any suggestions?)
15 Dec: Ibusuki - Kumamoto - Fukuoka
16 Dec: Fukuoka (We have plans here already)
17 Dec: Home

I understand that it seems like we are rushing the first 2 days, but we don't mind reaching the final destination for the day a little later (about dinner time).

I'm pretty lost because I didn't come up with the itinerary either..

Advice would be appreciated :) Thank you!

Advice is to slow down. You wont see anything other than from inside the car if you do the trip as planned.

You have 6 days worth of stuff to do and 3 days in which to do it in.

Most locations need a full day to explore 80% of the sights. You are attempting 2 locations a day.

Most locations are 2-3 hours away from each other. for example, you need to drive to Beppu, 2.5 hours in the morning, then spend lunch and afternoon/evening exploring sights.

Repeat for following day.