Any hotel that is near a streetcar stop is convenient for getting to Hiroshima station or Miyajima. Here is a link to the streetcar map
Hiroden Street Car Map. Here is a link to a page with a map of downtown Hiroshima
Hiroshima Navigator. Unfortunately it isn't very clear but you should be able to get an idea of how close everything is in the city center.
You will have no problem shopping in Hiroshima. In addition to the stores on Hondori there is also an underground mall, Shareo, and several department stores and smaller shops in the area right around Hondori. There are also a couple malls and other shops out towards the port on the street car line. Even Hiroshima station has several stores to shop at.