When our clients ask how they should dress their children for a family photo session, we tend to suggest staying away from busy patterns, but if done right, a mix of colors & clean patterns can look very cool.
Simple and comfortable is the key for fall. If your girls love dresses, we suggest these options below from Zara with a sweater and tights for warmth. Jeans or khakis for the boys with a long-sleeved shirt and or sweater in a neutral or earthy color will work with any home décor.
Colored cords are popular for girls and look great with a simple pattern or textured jacket. A collared shirt and sweater is a classic look for boys and a pop of color to tie in the look is great! We pulled these looks from JCrew.
Overall, we stress to our clients to work with a color pallet that they enjoy and not to feel pressured to match your outfits. I suggest taking one piece of clothing you love, throw it on the bed and then pull clothing for the rest of the family using that color palette as a guide. Remember, being to matchy-matchy draws attention to the pattern in the photo rather than the subjects in the photograph.
Have fun and be comfortable!