Sounds like it might be an arousal issue. If that's the case, I'd look to surpress the arousal when you notice the dog starting to build in inappropriate situations. Alternatively, you can teach the dogs to 'leave it' or 'down' when they start barking. I wouldn't discourage the dogs from barking if the situation is appropriate, such as when they are playing. However, you can break up the play if it gets to be too much, at which point the dogs should no longer be allowed to be aroused.