I think your best bet would be to analyze a peak fall foliage map and use that as a guide to what destinations you want to attempt to shoot. The maps typically use past data to give you a guide to the general time frame that colors are at the peak. They are not going to be solid dates every year, and weather plays a large part in the process.

You have to consider things like rain-fall as well as the low temperature to gauge if the peak is moving forward or backwards. Each states local weather authority likely keeps a foliage map online that allows you to view what percentage the current leaves are towards peak - but if you are planning a trip a few months out this will probably not help much.

I would first look at a historical map such as the one found on Storm Fax here. Once you have a general idea of the typical peak times, you can use a current foliage map such as the one that weather.com has here

As a general rule, locations with colder average lows and or higher elevations will be turning first - or in the first part of your trip. As you move to more temperate climates such as the west coast of Washington, you will find the peak is moved back towards the end of October.

If you are interested in specific parks or destinations, I would look at Flickr and find shots that took place in years past with great examples of foliage. Just make sure you consider more then one set/year because every year it changes.

Overall - any location throughout the northern US provides ample fall foliage opportunities throughout October. The key to getting the absolute peak will either require you to stay in a limited geographic area or be able to quickly move as the colors change while watching local maps. I think your trip has the potential to capture a great deal of the change in the seasons if you are prepared for one of the previous two options.