I find that our 3 year old is just way too tired at dinner time to be hungry. So we do dinner at lunch. Not always, but often, because today we did dinner at dinner time and he barely touched his food. He just wants a bath, a drink, and bed.

So, the way I ideally do it is serve their good hearty meal at lunchtime, and then if all he eats for dinner is a quarter of a sandwich and a serve of yoghurt, that's fine by me. I'm guessing as he gets older and isn't so dramatically tired at dinnertime we'll be able to do dinner at dinnertime again.