I frequently get asked by my clients what they should wear for family photos. I always stress that layers are important and add so much to the overall look to your photos. Adding scarves, jackets, or vests is a great way to layer. You don't have to be super match match either... try picking one or two base colors for the parents and then choose a lighter shade of those same colors for the kids. Prints in coordinating colors look great, too.
Need inspiration? One of the best tools for help is Pinterest! Check it out!
Search Pinterest here ---> http://www.pinterest.com/search/pins/?q=what%20to%20wear%20family