OK, so I am way in the minority on this one when threads like this come up, but we drew a hard line on this one after a year+ of things slowly morphing into "kid food" and "adult food". I just plain got sick of making separate meals/lots of components, or them grabbing a yogurt or cereal or whatever when there was perfectly good, not highly unusually flavored food being made every night for dinner. It started innocently with me fiixing a separate starch if the kids didn't like the one we were having, or a separate protein...and snowballed over the course of a year to basically making 2 meals every single night because I wa sjust too emotionally spent form other things to have drama at mealtime. But I got tired of it and felt like it was ridiculously privileged for us to be living like that and the kids expecting to hav ehteir favorite foods at every meal and snack every day.
So the lightbulb moment came one day when thinking about "not liking" food. The lightbulb was that you don't
have to like everything you eat. Some foods may not be your favorites, some you may not even like, but they are good for you and good fuel for your body and cooking and sharing a meal (not sharing a table with 2 different meals) is an important value DH and I wanted to pass to the kids. And we told htem EXACTLY that. We prepped them for several days that we would be changing things and had several conversations about food and likes and favorites and dislikes and things that truly are objectionable/make you truly ill. We would point out that maybe mommy wasn't in the mood for spaghetti tonight but it's what daddy made, and it's healthy and so I ate it and wound up enjoying it. Or that daddy doesn't like rice at all, but when mommy makes meals with rice he eats some because that is what's been made. None of the foods we make are unusual, so we just got to the point where it was ridiculous that they "didn't like" a chicken breast with potatoes and green beans and were getting a separate spread of food, so that's pretty much what they were given and what they had to eat. I made sure there was always one item they liked, and they only got a few small bites of the other things at first to ease them into it. But they did have to eat it.
I won't lie, it wasn't pretty for a few nights. There was LOUD protest from DD who was about 3 when we started this, and a few very LONG dinners. DS was a little over 5. We were sympathetic, but firm. In the beginning there was always one thing in the meal plan that they liked so they wouldn't starve, but they needed to have X # of bites of everything else, too.
Now, they both have some texture and flavor profiles that they truly, truly find objectionable and we do not force those on them - For instance, neither of them will eat casseroles, stews, or soups where there are a bunch of things mixed together in a creamy/liquidy medium, so we don't force that on them - they can have a PBJ or whatever those nights. I still, after trying dozens and dozens of times throughout my life, don't like fresh fish (I like shrimp, and tolerate lobster, but that's about it), and it's a texture thing - so I get that people can have true objections to some foods (but it's usually just a category and not MOST foods beign disliked) - and I also realize that some people have sensory issues or other medical reasons to not eat things. But for *most* people with no sensory/medical issues, having only a handful of foods you "like" I think has more to do with beign used to favorites and not pushing your comfort zone to broaden horizons, and less to do with actually "disliking" things.
Since we implemented "Operation Victorian Orphanage" (as DH and I called it in private), their horizons have expanded
greatly. Just today my 6-1/2 yo son picked out spicy shrimp sushi for lunch out today and GOBBLED it down, to the amusement of several families nearby.
For regular old meats, starches, and veggies not prepared in really unusual ways, they each get as many small bites as their age. If they want more of anything they have to finish all their firsts before they get seconds of anything. And we always have a salad/raw veggies with every dinner, which they both have loved since before they were 1 year old.
They get to select their breakfast, their lunch, and their snacks every day from their favorite foods. And they each have a "choose night" for dinner every week where they pick the dinner menu. So for just 5 meals out of 21 (+ 14 snacks) every week, they eat what we prepare whether it's their favorite foods, whether they like it or not...I don't think that's unreasonable at all.

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I feel SO much better about mealtimes as a family, and things are so much more peaceful. For several weeks every night before dinner we would prep/remind them about what to expect and what we expected from them. I was feeling really......excessive....about catering to their tastes so much, it just felt very privileged to me and I didn't like the value it was passing to them. This feels WAY better, and everyone is truly OK with the foods we eat. They occasionally might try to pull a fast one on us, but we gently but firmly remind them that dinenr is dinner and they have a TON of choice all week, and this is what's being served and is what we'll all eat.