I also can’t tell what is in the bowls beside Roy and his sons - to the top left of Roy’s plate, right hand side of Toby and top right of Brad’s plate. Maybe Ronnie and Silvia have one of these bowls too but I can’t tell. You can see Brad eat out of his bowl at one point and it looks like something pale (I wondered coleslaw or macaroni).

It looks like everyone at the table has a bowl on one side or the other. This was a time when a common middle-class American family dinnerware place-setting might include a salad bowl with a simple salad: chopped iceberg or romaine lettuce with a store-bough salad dressing (ranch, blue cheese, 1000 island, etc). Probably not the most appetizing thing in the world, but totally legit given the era and setting (with Roy being a electrical line worker).