Hi Bill -
First off - congratulations for a great showing at Rancho Cucamonga! (Sorry, they got mixed up between us - I hope you got your 3rd place stuff??)
Regarding Kennel Cough...
As you have read the posts I just had a bout of it with Emmy. Aside from that, I have NOT had a case in probably 10 years and I do NOT vaccinate against it. My dogs are out and about training and trialing ALL THE TIME, exposed at the dog park, shows, etc. It's not so much the exposure, from what I understand, as it is the dog's immune response. In our case, Emmy had a pretty tough training session before the Pet Expo (another sport), tweaked her neck at the show (maybe caused by stress, etc.), and it was unbearably hot that weekend. I let her heal at home for a couple of weeks, no trip to the Vet, no antibiotics. Neither of my other dogs got it, including one senior. It did mean we missed a bunch of training which was a pain, but it really is not that big of a deal.
It's entirely possible your dog (JoJo?) was a tad stressed from the event at Rancho Cucamonga. It was really cold, a new situation, water up the nose assaulting the sinuses, etc., that was the real reason he came down with it. I don't know that there's any way to completely avoid being exposed. As Wendy (Renegade) says, she brought it home on her clothes one time. KC is a generic term, like the common cold. It can be "caused" by bacteria, a virus, etc. I am not a Vet (and do not play one on TV!) but I expect JoJo may have a better immunity to that particular strain in the future.
If it were my dog, I would keep him home for about 10 days after he stops coughing. After that, I would not restrict his activities and just let him have fun. :-)