14 or 21 day JR pass

Hi,
I wanted to enquire whether I would be better off purchasing the 14 or 21 day JR pass for my upcoming trip to japan

Our current plans are:
December 31st - Arrive at Narita Airport
Dec 31st - 6th Jan - Tokyo, with day trips planned to Kamakura, Tokyo Disney and a restaurant in Hachioji (near Takosanguchi station on the Keio line)
7th Jan - Travel from Tokyo to Kyoto
8th - 10th Jan - Explore Kyoto, with a likely day trip to Hiroshima
11th Jan - Travel from Kyoto to Hakuba
17th Jan - Travel from Hakuba to Narita Airport

I'm wondering if we are better off buying a 14 day ticket and then paying for the trip from hakuba to Narita separately, or buying a 21 day pass.

Also is the ordinary ticket sufficient rather than the green ticket?

Thanks so much,
Natalie