Originally Posted by
worldjunky
... It looks like i can visit Nagasaki and Miyajima in a long day.
No, No.
Hiroshima and Miyajima are very close together and can be done in a day trip from Kyoto/Osaka. Nagasaki is a LONG way from Miyajima and you just cannot do them together in one day.
For your short 7 day itinerary, you should forget about Nagasaki. Leave it for another visit in the future.