Our approach was to lavish lots of praise on anyone at the table that ate fruits or veggies, and completely ignore all other eating behavior. That includes the adults, praise the adults. Act absolutely fascinated about anyone who eats fruits and veggies, discuss it with them endlessly.
You do this while you are establishing the habit. Less is needed after the habit is established.
If I kid says "I don't like spinach", then many adults will exclaim "You don't like spinach!" like it's the most facinating thing they ever heard. I think this is harmful. The statement "I don't like spinach" should be taken as a cue to praise someone else who eats spinach.
Also, you need to make sure each type of vegetable and fruit makes a good first impression. They need to be prepared so kids will like them. Don't worry too much about salt, sugar and fat at first. Salt reduces bitterness in veggies. Sugar can make a sour fruit sweeter, but just finding good sweet fruits is better, I guess. If you do this, then at least a kid will not come to reject a specific vegetable no matter how you prepare it. I have noticed that my grandkids all are willing to eat lettuce, I think that was because it had a good tasting dressing on it when it made it's first impression on them, because I don't think lettuce is better tasting than all the other veggies that they reject.
This worked with the 2 kids I helped raise from infantcy, but we practice this from day one. But, all my grandkids tend to be finicky eaters, and it does not seem to work particularly well or quickly in accomplishing a turnaround of an established finicky eaters.