The motivation behind the cooking, cleaning and dishes could be interpreted a couple of different ways. It could be seen as “since we’re burdening you guys so much, we want to make sure we are contributing in the way we can”, or “you guys work so hard and are such a good family, we’d like to make this gesture to show our appreciation of your efforts and ease your burden a little”. Alternatively it could mean “we consider the way your run your household to be vastly inferior: thank God grandma and grandpa can come over for a little while every year to set things straight”. I would strongly advise you to have a serious discussion with your wife over which is the most likely motivation, as that will dictate what your appropriate response is. Imagine if your in-laws view their cooking and cleaning as a “gift” and you’re screaming at them about household rules over how often meat gets served? How would you feel if you
By the same token, in-laws who feel that they can come into your home and run your household “their” way because you’re doing it “wrong” cannot be tolerated. It’s disrespectful to you, your wife and your son. If that is the case, then the only option is for them to stay outside of your house; book them a hotel or AirBnB right away. If they show up unannounced again during this trip or in the future thinking that you will let them stay, then you immediately sit them down at the nearest device and book alternative arrangements.
Assuming their motivation is one of the first two, then pick your battles man. Personally, I would have no problem letting someone else cook and clean in my house for a couple of weeks regardless of how they did it, but I would go absolutely nuts if my in-laws were using my house as a personal storage unit. Also consider what’s important to THEM, not just to YOU. If they consider it a really huge deal to make you and your family a home cooked meal, and consider it an insult if you don’t eat it, then maybe that’s one where you want to take a hit for the team.
I’m of a different mindset regarding the racist comments. I don’t feel that someone from an older generation who is otherwise a good person should be ostracized from loved ones for making comments that were considered acceptable for most of their lifetime. Use this as a teaching opportunity for your son. If I were in your shoes, I would teach him that everyone has good and bad things about them, and that you can still love someone even if you don’t like the bad parts of them. You can also teach him that even though someone he loves does, thinks or says something bad, that doesn’t mean it’s ok for him. You could also teach him that it’s OK to tell people that they’ve done or said something wrong. Your in-laws might react differently if your son called them out for a racist joke than if you do.
Hope this didn’t come too late to be helpful. Keep us posted!