My Dad Mixes Everything He Eats. What Do I Do About the Sanggyeonrye (In-Law Meeting)?

My dad has a habit of mixing all his food into one bowl for every single meal... He says he developed the habit because lunch breaks were too short at the factory he worked at when he was young. Regardless of the menu, he pours the soup over his rice, and shoves all the side dishes in there, too. He doesn't just mix vegetable side dishes; he also scrapes the meat off grilled fish and mixes it with the other sides, and even when we grill meat or order chicken... he unconditionally puts everything in and mixes it up.