Add some fruits and vegetables to your family’s sandwiches (ideally on wholemeal bread).
You can add some banana, sliced apples or strawberry slices to a peanut butter sandwich.
Top a turkey sandwich with lettuce, tomato, cucumber and anything else they will eat.
You can even make a Subway style vegetable sandwich by combining several different vegetables with some light mayonnaise and cheese on bread.
(Don't be too heavy handed with the mayo though )