Our goal for family photography is to present images that focus on the family without being distracted by their outfits. Simple, neutral, classic are all descriptors that come to mind. Patterns should be small and subtle. Try laying out everyone's outfits on the bed and see if they look good together. Try not to choose anything trendy that will date your photograph. Jewelry and accessories should be minimal.
With all of this said, this is your family portrait, and it should reflect what is important to your family. If you want to go crazy, go crazy!
For children and sibling sessions, feel free to bring a few outfits that showcase your child's personality as well as something classic that will stand the test of time.