1) Be yourself
Wear clothes that you and your family feel comfortable in. Photographs are meant to capture who you are and a lot of that can be communicated through your personal style. Also, keep in mind that if someone doesn't like wearing something (i.e. a dress, or hat) they will not look comfortable in the photos and probably won't have much fun.
2) Be aware of your surroundings
Wear clothing that goes well with your location. High heels are probably not the best option for the snow, or grass. Alternatively, you could wear a great pair of boots or wedges.
Wearing layers gives you more options. Jacket on, jacket off. You get the idea. Plus, it adds more visual interest and texture to your photos.
4) Don't let your clothes distract from you.
Ralph Lauren might be your favorite brand, but sometimes that logo is a little large. Don't let logos or t-shirts with any kind of drawings distract from your photo. Try to stay with solids, and patterns to create interest. Also, please choose more than 2 colors for everybody to wear. I think the best practice is to choose 3 main colors and let individuals choose from any of those shades. It worked for my wedding and it can work for you as well.
5) Check out my pinterest to see even more great ideas on color schemes, and all of the little details like how to roll your cuffs. And here's a link to a similar blog post I did a while back a few more tips for you next photoshoot.
Is there anything you find particularly vexing about preparing for a photoshoot? If so, let me know in the comments below. Happy November!