In this document http://www.dannen.com/decision/scipanel.html several leading physicists of the Manhattan project suggested that the US government talk with its allies about the atomic bomb before making any decision.
To accomplish these ends we recommend that before the weapons are used not only Britain, but also Russia, France, and China be advised that we have made considerable progress in our work on atomic weapons, that these may be ready to use during the present war, and that we would welcome suggestions as to how we can cooperate in making this development contribute to improved international relations.
Did the government follow these recommendations and make it clear to some of its allies what kind of weapon they had? (I remember being told they told them they had a more powerful bomb but were pretty vague on how powerful) Also do we know if these officials then contacted their own scientists to discuss this?
If they did, how did the allies react and did they make any suggestions concerning their use? (even if it turned out they underestimated how destructive it could be).
The US got formal approval for the bombing from the British, as was required by the Quebec Agreement of 1943. There was no real question of it being approved, nor was it any kind of surprise (the British had been involved with building it and the targeting decisions).
More contentious was the US plan to release the Smyth Report, which also required UK approval. The British physicists were very dubious but eventually assented.
Truman made a vague mentioning of a new weapon to Stalin at Potsdam, just after the Trinity test, which was as close as he got to telling Stalin what was going to happen. There are conflicting accounts, but generally speaking, Stalin feigned disinterest, and Truman thought he didn't understand. Stalin of course had known about the bomb project years before Truman was told about it, because of Stalin's spies in the program. He understood what it really meant, which was that the Trinity test was successful.
No other ally was told about the atomic bomb before its use. The French may have had some inkling, because one of the participants in the Canadian part of the Manhattan Project (Hans von Halban) was allowed to talk to one of their physicists, Joliot-Curie, after the liberation of France. It's not clear what he would have told him (and he was not in a position to know too much about what the US was doing, but he probably could have guessed; he claimed to have divulged no secrets), but it's not impossible he might have let something on. I don't think we really know for sure. Anyway, it was not any kind of official spread of information, in any case.