What is the best option 14 or 21 day pass

We are a family of 6 (4 adults and 2 kids 13 /11) travelling to Japan in Sept/Oct 2024 for 3 weeks.

I want to know what the best JR pass for us.

We arrive into Kansai Airport around 1pm and are staying near Umeda station.

In Osaka we plan to go to Hiroshima/ Himeji Castle. Nara Park and a few other acitivites near osaka

after about 5 days in Osaka when then travel to Nagoya for 3 days

in this we only plan to go to Legoland.

then to Tokyo from Nagoya for 10 days

in this we plan to go to
- Mt Fuji - Disneyland - Shinjuku - Sights around Tokyo. Tokyo tower etc.

Then we depart from hotel to Narita airport to fly home to Sydney