It's so confusing...

I have spent a few days looking at working out an itinerary and have used HyperDia to estimate costs but I am just hoping to get a second opinion.

I am travelling with my family in December 2018 (we are getting frequent flyer flights, hence planning ahead). There are 5 of us, with children aged 5, 15 and 16. I assume the 5 year old is free for all transport, please correct me if I'm wrong. We will be flying in and out of Narita and doing the following:
5 nights in Tokyo - 2 days of sightseeing and, of course, two days at Disney
Travel from Tokyo to Osaka - tossing up whether to stop at Hakone on the way to Osaka)
7 nights in Osaka - trips to Universal Studios, Hiroshima, Nara, Himeji and Kyoto
Travel from Osaka to Hakuba
6 nights in Hakuba - 3 days skiing, maybe see the snow monkeys, tossing up on Matsumoto
Travel from Hakuba to Narita Airport

From my research, I conclude that we should get a 14 day JR pass, starting from when we travel from Tokyo to Osaka. Is this correct?

Any itinerary suggestions are more than welcome.

Sherie