At home, we all eat paleo-style, and I don't hear any complaints! All of us have seen improvements, some way or another (except for our second son, who is only 1 year and has been paleo all his life, and who is very healthy). Still, I wonder, do children have different nutritional needs?
Can they tolerate dairy better (if they are under 4)? Do they need more of one or the other macro-nutrient? Is intermittent fasting something you would do (our kids don't)? Are there some foods that adults can handle, but kids can't? (ok, they don't drink the occasional wine we have) ...
[Our kids get quite a fair amount of fruit, and some starchy tubers (more than the parents). We are very strict on the sugars though, and recently even more on the grains. They get milk and dairy (mostly yoghurt)(full fat of course).]
Kids definitely have different nutritional needs...I think of their greater need for fats first. Directly addressing your other comments/concerns...
NEVER fasting for kids. In paleo societies, as well as some modern ones, children VERY commonly breastfed until age 4. There was never a lack of food for them. Even if a mother is starving, her milk will be adequate. Their energy needs are so great for growing and such rapid development, they can not afford fasting.
Dairy...they can NOT tolerate it better, if anything it is more destructive, especially under 2. If they are eating dairy, it should be RAW, full fat like you said, and CULTURED. Kefir, yogurt, etc., in small quantities, if at all. I am in full support of dairy free households. As long as you are eating animal flesh and getting proper protein and fat, you are missing nothing from dairy. The calcium argument is a myth.
Go grain free. At least gluten grains and rice free. There are seed "grains" like quinoa and amaranth. Not too much buckwheat though. Any baked good is from coconut flour around here. Occasional amaranth breakfasts or quinoa w/lunch. ALWAYS soaked overnight, eating with lots of fat. Even these have anti-nutrient properties, and dry starches are so irritating to the intestine.
I think it is awesome that you little one has been paleo all along. My youngest, now 2, has been as well, and his sisters are transitioning. We have always been grain/dairy free, and very aware of the sugars, but brown rice was a mainstay for them for a while. Stone, the youngest, is much more robust.
A general thought. Mother's milk is higher in lactose, and just overall thinner and sweeter than the milk of a cow. And it is also the case that mother's milk gets fattier and fattier over time. Applying the principles of paleo, this would suggest that newborns and infants need, or at least tolerate, more glucose than older children and adults, for this reason: it gets their insulin levels up and encourages the storage of fat. That way the babies get nice and chubby, a state of affairs that is advantageous for them. And then as the mother's milk gets fattier and fattier over time, this accomplishes a transition from higher glucose to lower glucose -- a transition to the diet we are supposed to be eating for the rest of our lives: high in fat and low in carbohydrate.
Just a theory, and obviously a little rough around the edges, but I wouldn't be surprised if it were true.
Seems to me, there are two ways to answer. Traditionally, I think kids would have gotten mother's milk plus whatever food everyone else ate. Overall, they would probably would not have gotten special foods, although there may have been specific traditions in specific tribes whereby certain populations, old or young, may have been given differential access to foods. In some tribes, older get the prime pick. In some, it is the men. In some, it is the women being courted by the men who get gifts. I have not seen any where children get the prime pick, but there are probably some like that too.
On the flip side, I am sure that children have specific needs that may be higher, as they are trying to grow instead of just maintain. CHildren may have specific cravings and stronger hunger because of this and they will probably naturally be drawn to more of the foods that will satiate those needs. So cravings might direct children to eat more of specific foods than the what the cravings of adults might direct them towards and children might become hungry more often. However, paleo is very nutrient dense and since we in modern times need not fear famine so much, paleo should easily be able to meet the needs of both children and parents alike.
If it were me personally, I would allow fermented diary and also allow milk when they are younger and just taper it off slowly as they age so it is not frequent later on. I'd probably go for the goat milk instead of cow though. If there were any signs of allergy in older ones, I'd nix the milk. I'd allow fruit in moderation. Usually, I think children will naturally moderate fruit intake if they are expected to eat the whole fruit instead of just the juice. THe whole fruit is more filling and satiating.
I'd allow starchy tubers as long as it was in moderation. I'd bet the kids are maintaining healthy weight naturally already but that is what I would be watching for anyway. And of course, make sure they get out in the sun a lot. Much of this is getting them into healthy habits in the first place so they will be able to eat healthy but still be social and still be healthy for a lifetime. Sounds like you are doing a good job if you ask me!