Hiroshima to Okunoshima

Hi! My daughter and I are very keen to visit Okunoshima. We will be travelling to Hiroshima from Osaka (hopefully getting an early shinkansen), leaving our bags at the hotel and then heading to the island (hopefully)! I am wondering what the best route is? Does the JR Pass cover the shinkansen from Hiroshima to Mihara Station - from there we need to take a local train, I think? We will head back to Hiroshima in the afternoon. Do you think this is possible? Thank you for any advice!