Personally, I wouldn't worry about it. I think if you have 14 year old boys doing any cooking that's a great start.

I don't know if this is sexism, or just an assumption that you can't
get 14-year-olds to do ANYTHING.

When I was 13, my mother was in grad school and I was doing most of the
cooking for the household. If they are doing the cooking, but not the
shopping, then it's pretty easy specifying what you want them to cook
as that's what there will be in the fridge.

If they are doing the shopping and cooking, I would follow the advice
above in terms of requiring several food groups.