The easiest way to get to the Miwa Shrine, the start of the both Yamanobe Trail and Mount Takakusa Miwa route trail, is by bus. There's the bus service from JR Yaizu station. Get a bus departing from #1 gate of the terminal. There's one or two bus services every hour from 7 a.m. to 8 p.m. Then get off at Miwajinja Iriguchi bus stop. Memo down the kanji of destination bus stop because all the info boards and announcements in the bus are in Japanese.
Sho'ouin Temple is the in the middle part of Okabe Stop. Kashiwaya Grand Inn is only a five-minute-walk away. To get to Kashiwaya go along the Tokaido Highway northward. If you are with kids there's is a park on the hill nearby. Five minutes walk south to Sho'ouin there's a park with Gochinyorai statues, another popular Okabe place. Either way the bus stops are about three hundreds meters apart. Then you can go back to either Fujieda station or Shizuoka station by bus.