definitely agree with the carnation instant breakfast/ ensure type drinks. we still give it to the kids, we call it chocolate milk, so they've grown up thinking thats what chocolate milk is. we also mix in blender with ice and call it a milkshake! but its nutritious and loaded with calories. its basically a meal replacement.
also, pasta, our girls liked pasta with tomato soup on it when they were really little,
and alot of people think this is gross, but mac and cheese with tuna mixed in, or elbow pasta cold with mayo and tuna.
quesadillas are good too, with cut up chicken and cheese melted in between 2 tortillas and cut into triangles.
english muffins with toomato sauce and cheese is a winner over here too,
and of course chicken nuggets and fish sticks but make sure its a good brand with real meat, some are all breadding and not very nutritious at all.
and you can always do breakfast for dinner... scrambled eggs and cut up sausage links, pancakes, waffles, eggs are really nutritious. oooh hard boiled eggs with butter mixed in, our neices call it "great grandma eggs" because thats the way my gram used to make them for us!
you can always make baked fries too, cut potatoes into little teeny bite sized wedges and bake on a cookie sheet (no frying) dont forget to spray the pan, dipped in ketchup
cottage cheese mixed with peaches, yogurt is always good too.