Making waves can be hard, so make ripples. Cook for them, if you can, more often. Set up romantic meals with the four food groups. Find ways that they like certain things cooked. If you end up ordering out, get pizza, with lots of veggies. It's not perfect, but at least you will be getting the needed daily alotment.
There are always ways of getting people to eat well or at least better if they have help without beating them over the head with a carrot.
Oh, and there are certain frozen dinners that do come with veggies now too. Or are at least healthier then fried or deep fried foods.