A.J.
Once I had to pull the "OK, but I cant' do anything" card with my in laws, and it was awesome, because the custom stuck. They were EXACTLY the same way. They came, wanted to be served 3 meals a day, never cleaned up after themselves, wanted to take their scheduled naps and walks and not be interrupted by the kids....only wanted to do things with one kid at a time, so I always had the others...etc. AND my husband would barely help because he was so busy hanging around socializing and drinking with his parents like he was also on "vacation".
Once they wanted to come right before I had a painting show and I was cramming to finish my painting in time. I COULD NOT have them visiting, and just had to hibernate and work, so I told them so. But they INSISTED because we were a stop along a big travel plan they had and wouldn't reschedule anything. So I told them and my husband straight up, "I cannot have guests right now. I cannot make any meals or do any cleaning, you have to pretend I'm not here. Sorry to be rude, but I will be in my studio with my door closed. If I had it my way, this visit would not be happening right now." I had the nerve to be that blunt because I was so mad at them for years of bad behavior and disregarding the fact that I said, "no" to the visit but they were still coming.
Guess what, they came, I stayed away from everyone and it worked out. I had to crack the whip with my husband about the kids, because he had full charge of them, but I reminded him what I had said, I could NOT participate. When he would say, "can you just watch" I'd say, "Nope, get a babysitter if none of you can handle the kids. I cannot help right now." Now they visit less, and they kept some of the habits from that visit, like more meals out, and they even got a motel once. I think their visit was too much work when I wasn't playing hostess, so they weren't in a hurry to come back, and they realized I don't like to wait on people (which I'm sure they hold against me but who cares).
So maybe you can come up with a reason you really cannot host, and stick to it even if they come. Otherwise, just cut them down to way less visits (5 per year??!!! I'd die!!!!) I don't know what's wrong with people, personally. If they can't behave, they don't get to come. Period.