This is among the most important pieces of camp gear. A good headlamp makes everything easier at night from tent setup, to cooking, to just using the bathroom. It is a must have for each member of the family. Quality matters as poor lamps drain batteries quickly and break during the abuse they are likely to receive as they are pushed into pockets, dropped, and packed away for months at a time.
Petzl and Blackdiamond make some of the best. Avoid the numerous cheap knock-offs.
Look for headlamps with a red light feature. Using the red light when flicking the light on for a short time will not cause your eyes to dilate.