Caravan

I agree with the consensus that making at least major point reservations is a good idea. Going off on a whim is usually great when it's just you and a close friend/spouse, etc. Going off on a whim with a group of people is much more difficult.

I have done caravans a lot - both short and long trips - and there is one rule I always make at the start of the trip: The person in the lead is responsible for not putting things between him/her and the others (e.g., racing around a truck before a turn off, rushing through a yellow light, etc.); the folks following are responsible for keeping up with the lead and not straggling behind. As long as everyone agrees to a general speed, that is usually enough to make for a positive trip.

For planning, I would have everyone agree as to what the max time in the driver seat should be between pit stops and what the max time should be for a full day. If in question, go with the weakest link - they are going to slow you down so you might as well plan at their pace.

If you don't want to plan everything before you leave, you can plan every 2-3 days as you go.

Every vehicle should have the day's destination before they start out each day. Everyone should agree that if they get separated, they will meet at that location (or leave a message there for the others) at the end of the day. Regular pit stops will prevent many emergency stops by one vehicle.

I wouldn't worry about always having everyone parked next to one another each night. The extra space may be enjoyable on some days. I do agree that if one person is making all the reservations, that pre-agreement about who gets which sites should be made.

Because the traveling will be pretty much a "we all go and we all go now" thing, that the days you are stopped should be left open as much as possible. This will allow folks to spend alone time as couples, deal with emotions, deal with headaches, backaches, etc. Don't insist on being joined at the hip at all times.

My last suggestion is to make sure you are all compatible travelers. It's very annoying to be a "we'll leave at 8 a.m." person traveling with a "we'll leave sometime tomorrow" person and visa versa. As one of the former type who sometimes travels with one of the latter, I know we annoy one another with our different styles. 6 weeks straight of each other on a trip like this and we'd probably not be as good of friends as we are. My being packed up and ready to go and her disappearing on a wander - or her enjoying a moment and my tapping my toes impatiently... not a pretty picture.