14 day or 21 day pass for this itinerary ?

HI Daniel,
greetings again. Still not clear on which pass to use on the following itinerary re days and when to start. This is my first visit to Japan and I'm travelling with my teenage daughter.

My itinerary so far is as follows:
December 3 Narita Airport terminal 2. to Tokyo (evening)
Dec 8 tokyo to Nagano and on to Yamanouchi (yudanaka station) for snow monkeys overnight
dec 9-11 Kanazawa (not sure if we do should take side trip on way)
dec11-13 Takayama
DEc 13 19 Kyoto (Including day trip to Nara)
Dec 19-21 Hirosima (with day trip by ferry to Miyajima )
Dec 21-24 Osaka ..( with possible day trip to mt Koya)
24 December Osaka to Narita Airport terminal 2 (Plane leaves at 7.20 pm so I think we have enough time to get there)
Should I get 21 day or 14 day pass?
Once I have the pass I have some questions about which trains to take in the Nagano/Kanazawa/Takayama area and whether I should include a stop at Shirakawa (bis?..does JRPass cover this)
Thankyou once again.
Kind regards Helen