I would recommend a day trip to Miyajima (but if you were willing to spend extra ¥ to stay overnight it's very worthwhile. The shrine is beautifully lit in the evening.
Please remember when staying in a Japanese style inn 'Ryokan', the price includes an elaborate multi-course dinner and breakfast - so factor this in when looking at room prices.
Staying in a Japanese ryokan at least once should be on top of your list. It's one of the main reasons to travel to Japan.
Just remember when staying in western-style business hotels these are just functional, small rooms with narrow double beds, not Queen or King size (unless you upgrade in standard to somewhere nicer such as the Granvia) At business hotels always opt for twin beds if you are traveling with your partner.
Also Japanese love bean filled pillows - this comes as a rude shock to tourists going by the hotel reviews, but you often get these pillows instead of western fluffy ones.
I hope you've read the Tripadvisor reviews of your hotel.
Things to see & do in Hiroshima
Peace Park & Museum, Shukkei-en Japanese garden, several art museums - the Museum of Contemporary Art is particularly good, shopping arcade & department stores, cafes, tram rides, eat oysters, okonomiyaki, locally brewed sake, watch a Carp baseball game.
Daytrips near Hiroshima:
Kurashiki quaint historic port town, well geared up for tourists, with excellent art gallery and good dining options for all budgets.
Iwakuni: picturesque historical area near Kintai-kyo Bridge well worth visiting for a day outing.
Sekkitei Japanese ryokan with lovely garden & onsen overlooks the sea, has lunch plans or afternoon tea options (you don't have to stay overnight) including use of onsen.
You might try Hiroshima Greeters Volunteer guides, this may be a good option for you