Jen, don't forget he probably really does have a headche.... But oh geez! He and my hubby sound so similar!!

But that's what I mean about chatting to him gently about your son's visit. Don't rely on him expressing his feelings. Perhaps instead begin by saying, "Now, I understand this may all be starting to stress you out a little, so would you like to come up with some ideas how we can ease your stress if it starts to get a bit too much? And set up some ways you can let me know you are feeling that way, so we both understand eachother better if and when it happens."

It will probably be better received if you say it is so he enjoys the visit, or he may think that you are doing it for the benefit of his son and not him. Remember when they need to feel secure it has to be about them (within reason).