Speaking as a parent that raised 2 kids, i can’t imagine not minding them and allowing a mess to be made.
I don’t “do” social media, but if I did, this mother would be told some “what for”.
There were a couple times my kids weren’t exactly perfectly neat at restaurants. Our tip reflected that and my wife helped clean the table.
Speaking as a parent whose child lived to eat put (still does) she was trained to behave. Even at home food on the floor is not ok. I don’t care the age