5 days, maximum travel

We are a family of 5, arriving Tokyo late June and staying in Japan for 5 days enroute elsewhere.
Our itinerary is to get south to Hiroshima area, stop up in Kyoto area, see Fuji area and fly out of Tokyo. We think that buying single use tickets will be nearly equal to a JRP. Would you recommend a JRP for each member of our family due to ease, or should we not worry and find one way tickets for each leg of our journey.