Just wanted to say that we made it to San Diego for the start of our road trip, with much help from Roadtrip America and the forum.
Family and friends at home in the UK wanted to be able to keep in touch and see how our trip was going, so we have a website which I'm trying to update in sections as we go. If anybody's interested, it's here - we've only just started the car journey.
Meanwhile once again thanks for this great site - it really helped with the planning of our trip. Any further advice gratefully received!