If you take your photos outdoors, avoid positioning your family facing the sun. Harsh shadows can ruin your subjects’ facial features. Ideally, photograph them during the golden hours (the first and last sunny moments of the day), or else place your subjects at an angle from the sun. If the latter is on a vertical axis, ask your subjects to lift their faces slightly towards the light for more even diffusion.
If you take your photos indoors on Christmas night, take the time to properly analyze the sources of light. Is it too dark? Are there many lamps on? Is the sparkling tree too much? Set your camera to the widest aperture, avoid flash and use your tripod for best results.