When thinking about colors consider using 2-3 complimentary colors instead of just one color.  You want to create a color palette with your outfits. If you do want to do matching outfits or exact matching colors that is also fine too, but a color pallet does photographer a little nicer.

Pick your color palette first.

If you are doing the modern setup whites, dark greens, blacks or cream colors would work. You can also add hints of red as well. 

If you are doing the classic setup whites, deeps reds, browns, creams, dark greens are all great options - avoid all black for this setup it is too harsh for this soft cozy look.

Any of those colors would work for both the outdoor or bow setup as well.

If you are doing all 3 setups neutrals would work best with a hint of maybe deep red or dark green. neutrals like tan, creams and whites.

please avoid colors like pinks, bright oranges, yellows, blues. stick with the neutrals or darker Christmas colors

If you are going to do flannel make sure the flannels match. I would reccomend only putting 1-2 people in flannel and the rest in solid colors to match. If you are doing all flannel pajamas that is fine to all match.

I do alway recommend avoiding logos and cartoon characters on children's shirts. unless you are wearing Christmas matching pajamas.

I usually would recommend men to avoid wearing any type of hats because of the shadow it cast on their face, but I know many men are more comfortable with wearing hats. Please just keep in mind to wear a hat that still matches the color scheme and has a discreet to no logo. Also keep in mind that I may also ask you to tip your hat up a bit if it is covering your eyes.