Did the bomb need to be dropped on people to end WWII?

My dad always said that the war could have been ended with the United States inviting a delegation of Japanese to one of the tests of the atomic bomb.  

Or, the United States could have dropped a bomb on an island off the Japanese coast - and announced the next bomb would be on a Japanese industrial zone. 

Instead, the US dropped 2 bombs in 3 days on densely inhabited civilian areas. 

Not the best decision in my opinion, but then I wasn't there. 

Associated Press photo here [1]on Google Images