Single way from Osaka Kansai airport to Tokyo Narita airport worths the Japan Rail Pass?

Together with my wife and two children (10 & 12 years old), I will visit Japan for the first time in my life. We should arrive on 18th of July, in Osaka Kansai airport and stay one night in Osaka. It is highly probable that we will visit Universal Studio in Osaka on 19th of July. After that, we plan to go to Kyoto and stay there for 7 nights, during the time maybe go to Nara as 1 day trip and go to Himeji as another 1 day trip. On early morning of 26th of July, we leave for Fujisan five lakes area and plan to stay there for two nights. It is highly likely that we will take a bus tour to Mount Fuji there and try to climb the mountain for a while. If weather does not permit, we can also take some sightseeing bus tours around the region.

It is planned that we will leave Fuji five lakes area on 28th of July and go to Tokyo. After staying and visiting Tokyo city for three days, we will catch the airplane at the night of 31st of July in Narita airport.

May I ask if my draft plan is appropriate for first time visitors in Japan and financially reasonable? Shall we buy a JR Rail pass during these 14 days?

Thanks and best regards,

Raymond