Back when I drove long distances, I had a few rules that kept me awake and alert. Some of these seem to work for everyone, some of them work only for certain people.
[ol]
[li]Ten minutes every two hours. Every two hours, stop somewhere, get out of the car and walk around.[/li][li]As little surgar as possible. Sugar gives you a short burst of energy, and those burst wear you down faster than you’d think[/li][li]Twice as much water or juice as caffine. You’re stopping every two hours anyway, and dehydration saps you more than having to pee does[/li][li]When you stop for meals, skip the fast food, get a decent meal at someplace with waiters. Don’t eat too heavily, but don’t nibble either.[/li][li]Know your limits. I could do 36 hours, but if I had to go farther than I could get in that time, I’d do 20 hour chunks, and then go to a hotel[/li][li]Don’t take naps (this may just be me), and don’t sleep in the car. A real bed, and a shower allow you to recover faster, and last longer.[/li][li]Avoid the sun. Try to plan your breaks so that you don’t end up driving with the sun in your eyes. Personally I like to start such trips just after sunset, and to find when the sun starts forcing me to use my visor (heading west). Means I’m freshest in the dark, and not squinting (it’s too easy to close your eyes when you’re squinting and tired).[/li][li]When travelling in multiple vehicles, my rule is to agree on a max speed, and the lead car must always keep the last car in sight. This is to prevent a masshole like me from losing someone who isn’t used to heavy traffic or high speeds.[/li][/ol]
From some of what you’ve said, I’d also advise either getting push to talk on your cell phone, or buy walkie-talkies and use them instead of the phones. Also, plan everything, with modren map access, you should be able to figure out what rest areas and towns you’ll be likely to stop at, so lay it out at the beginning. Have very specific rules in place for what to do when/if you get lost, or slowed down by something unpredictable. When you’re tired, having rules helps you avoid making dumb decsions, like trying to go another 60 miles to get to the hotel you wanted to stay at. It also helps facilitate communication,
One hand off the wheel isn’t an issue, providing that one hand is always on the wheel, and you have the personal discipline to drop whatever’s in your other hand should you need it (yes I have dropped my drink all over myself because I suddenly needed extra control, better soaked with soda than soaked with blood). Eyes off the road, though, is a big deal, so make sure you can manage the air flow and radio without looking (my radio can be somewhat controlled from the steering wheel anyway).