So, why allow it? "Sorry, that doesn't work for me." Or, are you OK with it after all?
As to why? Maybe he is simply trying to be a decent parent and help out when the kids are sick and you are sick. It is a sign that he feels enough space from you and little enough pressure/blame that he is now able to do something nice.
So, shooting down his generosity will take a step backward from that place, probably. Because it would be about blame and anger. This is OK, just thought I'd point it out.
Remember, this stuff is YOUR CHOICE. You don't have to accept dinner from anyone in your own house if you don't want to.
