I think it’s easiest if you let each driver go at his own pace and not worry about staying together. Just make sure everyone knows the route and use phones to communicate. If there are certain places you want to visit on the way, tell the other driver that you’ll meet them there.
Just to satisfy my curiosity: What do you want to achieve?
Put the slowest & safest driver in the lead car and tail them.
Most of my problems come from spur of the moment drives where 1 or more drivers insist on just following without any communications or maps or GPS or an extra person to help watch or they are extremely slow drivers that make you pull over every mile or so to let them catchup without totally losing them.
Anything over about 5 miles, they at least take someone who knows the way with them or they are on their own.
If the leader is not very good or thinking about the fact that he has a looooong car that will more often than not try to do something stupid and be ready for any & all, someone will get lost anyway.
If the driver of the lead car has a lead foot, require that they stop every 50 miles and perform a Chinese fire drill. This should at least give the trailing car a fighting chance to catch up.
In some places, pulling off to the side of the road is a big no-no and a largeman with a gun will tell you to move on.
I’d go with an antenna marker - and, for super-cool: find old C-B Radio Whip antennas - those are 6’ long and clamp to whatever.
I can almost guarantee you will be the only ones within 500 miles of each other with those.
If you do get separated, have a list of exits (one every 100 miles or so) with specific brand of gas station or fast-food joint.
If you lose sight of each other, pull into the next stop on the list.
Of course, have your lights on 7/24.
People have been doing convoys for years before CB came along, now cell.
Real transceivers (walkie-talkie) work just fine - they also cost a fortune.
I went to a DDS once - the guy before me came out and produced 3 different comm devices - 2 cells and a transceiver. One cell and the transceiver were employment related; the other was a personal cell. The one he identified as “the one I DON’T mind answering”.
I recommend car flags. Around here it’s purple ones with white letters that are an anagram for “Real Fun”. To get some, just keep some nice clothes in your car & when you see a hearse in front of a funeral home pull in & say you are going to the cemetary. After getting your flag you can:
[ul]
[li]Leave[/li][li]Stay & go in & express your condolences. Make sure to sign the guest book. (This has the added benefit of being a fun game later on for the grieving family. It’s call "Do you know who the ___ John Doe is & how did he know Aunt Ethyl?) ;)[/li][/ul]
The extra benefit of these flags is that your trailing cars can legally go thru red lights to stay with the [del]pace[/del] front vehicle. It’s legal as long you keep a box & a shovel in the trunk so as to properly dispose of dead cat antenna topper when you arrive at your destination, which is aerodynamically inefficient & therefore a deficit to your MPG numbers.
Or, I recommend Glympse smart phone app (if you’re in coverage areas). Another app, Zello essentially turns your phone into a PTT/Nextel phone.
One of these.