Remember that a nutritious meal need only have a small amount of protein along with some fruits and/or veggies. The protein can be a small amount of meat, or it can be a combination of dairy and grain such as a cheese sandwich, or it can be dried beans. A starch such as bread, potatoes, or rice can add filler if your family needs (or wants ) a heavier meal.
One quick and easy one-dish meal would be to add any leftover meat to bagged salad. If you don't have any left-over meat from the day before, open a can of chicken breast or tuna.
A grilled cheese sandwich served with tomato soup makes a complete meal.
A peanut butter sandwich with apple slices (or fresh grapes or celery sticks) on the side makes a complete meal.
A scrambled-egg sandwich served with fruit would be a quick choice.
Another quick and easy one-dish complete meal: Cut up a couple of chicken breasts (half-thawed meat is easiest to slice), cook the bite-size pieces in a skillet with a little olive oil and add whatever fresh or frozen veggies you have on hand, season as desired, and stir-fry until done. You could serve this "as is" or with rice or some other starchy vegetable.