define hard? as kids mature and explore independence they try out all sorts of power-grabby, controlling things and food is an excellent vehicle for this. doesn't matter if they eat primal or sad.
until a certain age, they can only eat what's in the house, right? as they get older, yes, they make their own choices elsewhere, but that's true of anything they do in school or with friends. all you can do is set a solid foundation.
on a food board i frequent, a mother was recently bemoaning that her 4-year-old won't eat typical "kid's foods" that get packed for her lunch. the mom sends along pasta salad, granola bars and trader joe's ravioli, all of which come home mostly untouched. when she sends some left-over chicken or steak it gets devoured. the mom was not connecting what the kid actually liked vs. her own perception of what kids "should" want to eat.
As I ate the oysters with their strong taste of the sea and their faint metallic taste that the cold white wine washed away, leaving only the sea taste and the succulent texture, and as I drank their cold liquid from each shell and washed it down with the crisp taste of the wine, I lost the empty feeling and began to be happy and to make plans.
– Ernest Hemingway