JR pass?

Hi

We are travelling to Japan in Dec - 3 adults 4 children age 12, 7, 5 and 1.
Not sure whether should we buy a JR pass or should we not.

Narita - Kansai - Hakuba Tokyo - Narita

1st day - Kansai Airport
2nd day - Osaka sightseeing
3rd day - USJ
4th day - Travel to Hakuba
5th day - Snow Playing
6th day - Hakuba sightseeing
7th day - Travel to Tokyo
8th day - Tokyo sightseeing
9-10th day - Disney
11th day - Travel to Narita