You've already had some good suggestions. Also, realize it's okay if they vomit. Not fun for you, but that's their body's way of eliminating the mucus. I would also try kids chicken soup, the salt helps ease their irritated throats and coughing.
BUT, DO NOT GIVE COUGH MEDICINE TO ANY KIDS!!!!!
I have a friend whose 16 year old (yes, 16 yrs., not 16 months), almost died last year, because the antibiotic he was given combined with the cough syrup suppressed his brain and body functions to a point where his heart almost stopped and he was almost in a coma. It was only his first dose! And it was the correct prescribed dose. If they had listened to the doc who said just have him rest, and not taken him directly to ER, he would be dead. Some people, especially kids, have some sort of weakness to these medicines (which are often given together), and the results can be deadly. That's why so many doctors are saying not to give kids cough medicine now.