Feeding my elderly cats! ?

My 2 cats are 13 years old. They are finicky eaters and sometimes vomit (once or twice a month) but are always hungry. Both have been checked out twice by the vets. They have recently started muscling in on the dog's food (poor dog is quite bemused). Should I move my cats on to Senior food - is there something in the dog's good (standard Butchers Variety) that they feel should be in their own food (presumably the dog's food is more vegetarian based)?