Hi, Fern. Our family (myself, Mr. and a 13-year-old daughter) all eat the same way for the last 6 years, and everyone is thriving. We started down this path due to a variety of health issues: anxiety, obesity, skin anomalies, digestive distress, impaired immune function, headaches, SAD, and more.
I don't cook non-keto foods at all.... we are a sugar/grain/starch-free family... and eat very limited dairy. The only difference between us and our daughter is that our daughter eats fruit (I don't eat any fruit), and she eats as much and as often as she wants. Her own carb levels go up and down, depending on her activity levels... and generally her grams of carb per day are a lot higher than mine (maybe triple?)... though I've never tracked her food intake.
Some days (depending on her activity levels) she eats all day, and other days she eats next to nothing. During the school year she eats three meals a day, but as soon as school is out, within a day or two, she drops down to two, and if she's really being a slug, she'll eat only one meal a day. I like to think that what I'm watching is a properly working metabolism in action.
Additionally, our daughter has beautiful skin (no acne issues at all), never moody, has no hormonal/PMS issues (unlike her freinds), has tons of energy, amazing body composition, and is very strong... the parents of her peers often comment and wonder why their girls seem to be less muscular and tending toward getting heavier, while my Divine Miss O just keeps humming along.
Teachers have also noted that our daughter doesn't have any of the distractability issues and energy slumps other kids have... they are very aware of how different her lunches are from the others, and feel there is a correlation. They often say they wish all the kids at school ate the same way.
The thing with transitioning a family (kids in particular) to a keto compatible nutrition model, is that initially you need to be prepared for them to eat A LOT. Until they are fat-adapted, they will be HUNGRY, and unless they can eat freely, things won't go well. When we began, I made sure the fridge/pantry was FULL of on-plan food (hard-cooked eggs, nut butters/celery, cooked roast, pork rinds, pepperoni sticks) and I cooked more than usual for every meal and just let everyone eat when they were hungry. It took about a month, but then things settled back down, and appetites returned to normal, and even decreased.
I also don't cook non-plan foods for guests... I just make sure there is lots to eat, and no one has ever gone away hungry or complaining... in fact the exact opposite, LOL!
Dr. Jason Fung: "Holy consensus, Batman. With so many 'experts' from Michelle Obama to the USDA to virtually all of the medical professionals (including doctors and dieticians) agreeing that 'Eat Less, Move More' is the way to go, you might think that it is 100% unquestionably true. But here's a queer thought... if we all agree that we know the cure for obesity, and we've spent billions on educations and programs - why are we getting fatter? In other words, why does this 'cure' suck so bad?