Anne, I'm so sorry you have to have this procedure and wish you a speedy recovery! I agree with PPs that DS can't help the fact that he can't change his work schedule on such short notice, but also agree with those who say you're sensitive about it b/c you're feeling vulnerable. I'm sure once all this is behind you, you'll see things in a much better light.
It's lovely that DS and family live right across the street! I get the impression, however, that you feel that should mean you can just pop in any time you like. Not necessarily though - some people hate drop-ins! I know I do. Perhaps you're ok with them, but DS/DIL might not be. I don't think it's any worse to have to make a date to see them when they live so close than it would be if they lived at a distance. Please just enjoy the time with them that you do get.
Meanwhile, I also feel for everyone else here who has been through this kind of operation or had to see a loved one through it...