I read a book once about survival and they said "the difference between a food you like and a food you don't like is 24 hours." In other words, if you're hungry enough, you'll eat -- people that are lost in the woods eat bugs and things, right? And another thing I read said that if you put a food on a kid's plate enough times (I think it was 10 times) they'll try it after a while. All kids eat the foods that are popular in their culture, whether it's spicy foods, rice, lentils, whatever .. because they simply keep having it put on their plate over and over.
Based on those two principles -- if they're hungry, they'll eat it, and if they see it on their plate regularly, eventually they'll eat it, we made this plan for our picky eater daughter.
She didn't HAVE to eat anything. However, she had to have a piece on her plate of everything I made, and she could not have an alternative meal. If she refused to eat what I made, fine, but she could not have any snacks or anything later. And I'd tell her -- when you get hungry enough, you'll eat the good food I made you. Eventually she would eat the food I made, and now as an adult she calls me and asks me how to make the things she used to refuse to eat. And, as a bonus, she's a normal weight person in an obese family. I believe that is because we just didn't make an issue of food. Here's the rules -- simple -- eat or not, it's up to you.
It worked for us.
Also, don't get fooled by amounts. I'm a pediatric nurse, and I can tell you that kids need less food than their parents think they do. They will not deliberately starve themselves, unless there is some pathology going on. So if the kid drinks milk, eats one or two peas and a bite of chicken, and they're done, so be it. That may actually be all they need.
Just try not to let meal time be a battleground. Set out the food, serve the children small helpings, and try to not pay attention to what they are eating. Focus on chatting with one another and making the meal enjoyable. Meal times are not just for eating, it's also an important time to socialize as a family.