You have your grandchild all day once a week and you are on here moaning about not having them overnight?!
Your DIL or son can pick up their child early or miss weeks or cancel days, as long as they have the courtesy to let you know, for pretty much any reason.
As the child gets older they are going to mix more with their peer group too, you really mustn’t get too attached your routine.
You sound incredibly entitled, even if your grandmas behaved as you are doing, you should be aware that it’s not the norm, and unless you are brilliant at keeping a lid on it around your DIL, she probably finds you very difficult.