When we got our toy Pomeranian last spring he had kennel cough and some other illness from the shelter. We had another dog who didn't get sick at all as she is very healthy. We called the vet (we live over an hour away) and he suggested an antibiotic that I could buy at my feed store. Of course the meds didn't help the cough one bit, but it did take care of the other illness that was keeping his immune system from being able to fight the cough.
The vet told me it usually only affects dogs whose immune systems are already compromised (much like those who aren't taking care of themselves are more likely to get a cold, I suppose.) if you are concerned about your dogs, by all means, stay away a bit longer, and take precautions not to spread it when you do visit. Like a cold, it can turn to pneumonia if it isn't treated, which is why I went through the mess of giving my dog shots twice a day for over a week. The dog who has the cough ought to act perfectly fine and healthy, other than the cough. If he is acting sick, he's got something else in addition and may need antibiotics.