Katrina,
We've done two such trips. About 6,000 miles each, taking 3 to 4 weeks. A couple of thoughts from experience:
1. I don't remember if you said you had kids traveling. We had four each time, but they are great travelers. We would frequently do a 12-hour day to get to the next spot and they were happy as clams. If your crew can't take that type of travel day (or two), plan your stops accordingly.
2. We never planned out ahead too much. Because we had the kids, we wanted to stay in parks that had pools and such, so we generally used KOA or GoodSam Parks. We were able to decide a day or so before being someplace to make a reservation. If they were closed, we'd find something else. This allowed us to linger in places we liked.
3. You'll not see everything you plan to see. (see #2 above)
4. Plan some longer stays every few days of moving. This gives your family a chance to catch a breath and relax, without having to "do" or "see" anything. Just camp and have fun for a day now and then.
5. Driving here in the East is much different than out west. Lots more traffic and many more exits. Just take your time and plan ahead for where your map will take you.
Doing such a trip is a fantastic way to experience the country. It is our family's fondest memories.
