Be warned: RedCell = ENERGY! If he's not exercised thoroughly daily, it will make my extremely mild-mannered boy insane. Don't start feeding it until after your horse is well settled in. Feeding it during the trip would be a bad idea. ;)
Shipping boots are a good idea. Also, make sure your trailer is deeply bedded, and muck it out daily. If you don't already have a hay bag, you should purchase one and keep it stuffed full (even if it's only with low-quality grass hay). Take a ton of your current hay with you so you can transition over to the new stuff. Make sure you're stopping frequently to give your horse water, and if he or she might get stressed and not want to drink, bring electrolytes along and add it to his or her grain.
Hand walk your horse every day, and make sure you have your route planned out, including stops and places to spend the night.
MAKE SURE you have a complete and well-supplied vet kit, tool kits, plenty of feed, etc. Spare tires are a must. Getting a kit of fleece lining for your halter is always a nice thing to do for your horse, but isn't truly necessary.