Have you tried giving them 'dipping sauces' for their veggies etc. My 2 love having gravy in a small bowl and they dip in their veggies and eat them like that. I found them much more willing to eat when there was some kind of sauce available, gravy, mayo, tom sauce etc.

I am pretty lucky in what my kids eat, but we go through days when they won't touch their dinner, and I havve just learnt to let it go. We found really cutting back the afternoon snacks makes a difference, they usually have a snack when they have finished resting about 2:30ish, and then generally they dont eat again till dinner time- this has made a huge difference in what they eat at dinner time.