Advice for Travelling in Japan

My husband and I are planning a trip to Japan this Fall; arriving in Osaka on September 28 and departing from Tokyo October 15th. Tentatively staying in Osaka for 4-5 nights with a day trip to Hiroshima (most likely a booked tour); then to Kyoto for 4-5 days and then to Tokyo for the remainder of our stay. Planning a day trip from Tokyo to Hakone / Mount Fuji area (most likely a booked tour). Should we consider a JP Pass? If yes, should we get the 21 day pass even though we aren't staying 21 days/