I'd say it depends on where you are going and what winter means there. I personally would not go very far with kids in winter, because here it means very deep snow, subfreezing and sometimes subzero night temps, and the margin for error is slim. I would sooner take them to where 3 season camping is possible in Nov - March, fortunately Californians have lower elevation regions along the coast where snow is minimal or nonexistant. Snow gear and having multiple adults to play sherpa would be important for safety and accomodating the increase in gear/clothing for harsher conditions.