Travelling in January 2025 for 10 days --> Which Pass should we get?

Hello!
We are a married couple from Melbourne Australia, planning to take our 6 year old son, who has ADHD, for his first trip to Japan. We all love travelling for the fun adventure, discovery of cool/ interesting new things, pleasant surprises, beautiful sceneries and the special cuisines, and we love Japanese food! My husband and my son love hi-tech (IT/computer/technology) and train rides, so they are looking forward to learning more about Japan's railway networks and the exciting high-speed bullet trains. But unfortunately, they could get overwhelmed easily with/among crowds. And thus, we have decided to visit less crowded places in Japan in January 2025, and it is imperative for us to have a realistic plan with simple itinerary/ routes, i.e. not too many places to cover per day and staying at one place as a base for a few places to visit to minimise the luggage carrying trouble. As we will be travelling on a budget for barely10 days, we would like to focus on Kyushu, Osaka, Kyoto, Nara and surroundings, including Nagoya if time permits. We do not plan to ski nor do any hiking/ mountain-climbing nor any water sports at any beach. So please kindly help us with itinerary check and recommendations on places to go/visit with public transport (least trouble) and value for money.

Wed 8 Jan 2025 22:30pm: Depart Melbourne
Thu 9 Jan 2025 12:10pm: Arrive at Kansai International Airport T1
Thu 9 Jan 2025 15:00pm: Depart Kansai International Airport T2
Thu 9 Jan 2025 16:25pm: Arrive at Fukuoka Airport

Our main concern here is: Do we have enough time to check out with our luggage (checked-in baggage), move from Kansai International Airport T1 to T2 and check in for our next flight to Fukuoka? We only made this decision to fly from Osaka to Fukuoka recently, just to save us time and money.

Thu 9 - Sun 12 Jan 2025: Staying at FUKUOKA (3N)
Fri 10 Jan: Scenic Train Ride: ASO BOY! Mt Aso & Kumamoto.
Sat 11 Jan: Scenic Train Ride: YUFUIN NO MORI

Sun 12 - Tue 14 Jan 2025: Staying at KAGOSHIMA (2N)
Places of Interest: Kagoshima - Siroyama Observatory, Sakurajima Nagisa Foot Bath Park

Tue 14 - Thu 16 Jan 2025 : Still Uncertain --> OKINAWA or NAGOYA? (2N)
Places of Interest: Okinawa Churaumi Aquarium, Nagoya Legoland, Toyota Commemorative Museum of Industry and Technology, SCMAGLEV and Railway Park

Thu 16 - Sun 19 Jan 2025: Staying at OSAKA for Travel OSAKA - KYOTO - NARA (3N)
Places of Interests: USJ Mario World, Osaka Aquarium Kaiyukan, Kyoto SAMURAI & NINJA MUSEUM, Nishiki Market, Monkey Park Iwatayama, Todaiji Temple & Nara Deer Park

Sun 19 Jan 2025 10:10 AM: Depart from KANSAI International Airport T1

With the above itinerary, should we get a Japan Rail Pass for 7 days or JR Kyushu Pass for 5 days?
We will really appreciate any helpful input/practical tips/recommendations for our itinerary, means of transport, fun places to go/visit (including special dishes/cuisines to try) as a family of three. Thank you.

Yours truly,
Michinta