How can I politely ask in-laws to cover their coughs around my kids?

My in-laws were visiting over the weekend. My father in law sounded congested when they arrived, and he coughed all weekend without covering his mouth. It really bothered me, since I have three very small children, but I didn't know what to say. My husband is usually good about bringing things to their attention, but I think he gets tired of constantly reminding them of their rude actions. (When they visit, they are often loud and leave stuff all over the place when they leave. My hubby has commented on it several times, with no improvement.) Now my middle child and I are both dealing with colds. I'm trying my best to keep the other two well, but I can't stop thinking about how this could have been prevented if my father in law had been considerate while he was here. What are some polite ways I can remind a grown man to cover his cough next time? (Hopefully there won't be a next time!)