In extremely cold weather survival depends upon keeping the head warm.
If you are out in the wilderness with your children ensure that in the backpack everyone has a form-fitting wool cap or balaclava, as well as a scarf in the backpack. Even if you don't need this in the daytime, If trapped at night in sub-freezing temperatures this accessory can be a matter or life or death.
Only fools wear short sleeved shirts in the wilderness. Long-sleeved shirts with rolled-up sleeves if necessary.
Remember that daytime temperatures and night time temperatures, especially if there is a snowstorm can vary significantly.