Family of 6 on Japan Rail Pass

hi there,
we are travelling to haneda, tokyo arriving 21st december, then travelling:
23rd dec tokyo - Nozawa onsen
6th Jan Nozawa onsen - Kyoto
9th Jan Kyoto to Haneda Airport and Home
I was going to get a 21 day pass for all 6 of us (5 x >12 years + one child) but I was wondering if it would make more sense to get two 7 days passes instead at the beginning and the end (I'm thinking we won't be using the trains too much whilst we're on the slopes?).
Interested in your feedback!
thank you!