This link give good advice. Seems you have done all you could to prevent spreading. What we do it to put a notice on the door to say if anyone has a dog that has been coughing NOT to enter the hall and do not return for 3 weeks. The incubation period is ten days, so most dogs pass it on without their owners knowing.
Once they have had it they often get immunity so even within a household of dogs some will not get it again. Unless the dogs are very young or very old it is not usually life threatening and can be easily treated with antibiotics, and benylin is a good soother for coughing dogs (childs dose). Although called kennel cough it can be caught anywhere dogs mix and is air borne, so can be carried home on clothes etc.
Normal hygiene precautions are usually enough.
http://www.kennelcoug...el-cough-symptoms.php