You have a shoot planned, so now the important question is, what do I wear? I tell people first of all, wear what you feel comfortable in. If you aren't comfortable, you wont look comfortable in the pictures. If you like wearing jammies, wear jammies... they are your pictures, personalize it. What I typically suggest is to not be 'matchy matchy', ie the same sweater for every member in your family. Here are a couple suggestions that other photographers have given in the past.
Wear colors to compliment each other, try to stay away from all white (esp if you have darker skin). Any questions, let me know!