The dates have not been announced, nor have the specific locations, although rumors are certainly flying through the press. For the time being, all I know for sure is that he's coming at some point later this Summer. Different publications have announced different dates and itineraries for his visit - proof enough I think that no one really knows anything for sure at this point!
As soon as anything is confirmed I will post it here, but for now I'd urge you not to take too seriously any specific information you hear - when it's real it will be announced by the campaign.
In the meantime, if you want to show Barack how excited you are that he will be coming to our "green and pleasant land" there are a few ways you can do just that: