
As already said, you can really only treat the symptoms if it's the viral KC. I have in the past, used Benelyn, small dose, rather than childs Beneyln? The good news is that although this is like human flu, and mutates, usually dogs who have been vaccinated shake it off fast. It will affect puppies and the elderly most however, so if your pup is 4 months, it may be best to involve your vet. Vets prescribe a/bs to help prevent it going to pneumonia, which obviously, is more serious. Whether your other dog goes down with this would depend on his immune system - I don't know of anything other than vaccination/boosters to stop this being passed on, unfortunately.
Too bad about your holiday - but please don't bring them to a holiday location even for a week after the symptoms have gone - I live in a N.Cornwall coastal town and right now, it's FULL UP with people and their dogs. I tend not to take mine anywhere near the crowded town during the holiday season - who knows what's being brought in!!
If you have to get to a vet - again PLEASE don't walk the dog into the waiting room. I have seen this happen, and never seen an area empty as fast! Keep him outside (in the car).