[gambiting]

I really wouldn't be so sure. Even after destruction of Hiroshima and Nagasaki, the Japanese military still opposed surrender, in fact the day before the Emperor was supposed to announce it there was an unsuccesful coup attempt to prevent it.

So no, I don't think just detonating the bombs "harmlessly" would have have had the same effect. In fact hitting a target just slightly off the mark(like Tokyo Bay) would have been presented as American incompetence and failure of aiming.