As a relative newbie (only 1 really long trip) the thing I would add is the Good Sam website has a trip planner function that allows you to plan your stops and will show you Good Sam parks and others. Most have websites and the reviews can be really helpful in choosing a spot. Keep an open mind when reading reviews, it seems some people expect rv parks to be the Hilton and while we all like clean modern parks descriptions can very.
And like the others said, it's vacation so relax and don't stress, if something has to change just make the change work for you. Get some track books to find those places to see stuff that are not advertised. Off The Beaten Path is a good one. For instance did you know there are wagon ruts from the Oregon trail in Wyoming? They are definitely a ways off the path but we'll worth seeing.
Remember it's not the destination it's the journey there.