Tips
One “theory” I usually go by when planning my own family pictures is that all “neutrals” (i.e. black, white, tan, grey, and jeans) were acceptable but then pick one additional color to go with and any shade of that color (for the most part) would be fine. You could also use a secondary color as a pop. As an example this past year we chose green (all shades within reason) and coral as our pop. It looks nicely coordinated without being matchy.
Additionally, I’m huge on either getting my hair and/or makeup done for the pictures since I’ll have them on my wall for awhile. At the very least, I always have false eyelashes on (you can get them at Safeway with a self adhesive for about $6 by Revlon). I find they really help to frame the face and get my eyes to stand out. I personally always go heavier on the eye makeup (more smokey) and lighter on the lips. It gives a more natural tone to the pictures. But some red lipstick for Christmas cards will look fantastic as well! Mostly I think it’s about the confidence in rocking your look :)
Great article on choosing attire:
http://www.meghanowensphotography.com/what-to-wear-for-family-photoshoots-the-three-colors-pop-rule/