Reducing the Stress when Transporting Horses by Road and Air | TheHorse.com
Hopefully the link I just posted works for you (you might have to copy paste). It was just put up on The Horse recently and I thought it was an interesting read as I just finished a 30 hour trip with three horses today. Don't let the article worry you though!
We've hauled horses distances of 14-24 hours often over the past years. My dad is old school and relaxed about it - the horses get loaded, stay loaded, might not get offered water (he says they rarely drink anyway when travelling which I've found to be true too) and get some hay tossed into the trailer at night. He's never had a problem.
I, however, with my own three horses unloaded each night and let them eat hay or graze on a line and walk around a bit for a few hours. The trip was split into 3 days with 2 nights on the road. Unloading is RISKY though unless you are in a very safe place. I drove down some back roads and unloaded there... but even then, I put the horses back in the trailer for the night for peace of mind.
They were offered water several times but probably drank less than 5 gallons each over the trip. We stopped often to let them stand in the trailer. That's often enough of a "break" for them.
Ideally they'd have a hay bag to munch on in the trailer but I have an open stock trailer and worry about hay blowing around.
Other than that... I wrap legs sometimes, but only if it's easy to access each horse to re-wrap if needed, otherwise it's more hassle than good.
My three are down in the field now - no signs of illness or stiffness. The only one who is a bit worse for wear is my mare who pulled back in the trailer and scraped up her forehead on the roof ugh.
If possible, I would try to contact stables along the way and arrange places to stop where there are proper pens or stalls. A LOT less scary and stressful than spending a night on the road like we always have to!