Good Morning! It looks like you've got all the best advice already, but I'd really stress the trailer loading practice ahead of time if he hasn't been loaded since you got him. Believe me, a bad trailer loading experience can last a lifetime. I have a horse that's living proof. Take it slow and don't rush him. A little grain in the trailer always sweetens the deal. If he does ok, that's great, but if he's nervous or balky at all, you might want to feed him in there for a few days ahead of time. I like to put some hay in there with them if I'm hauling for any length of time. It gives them something to occupy their mind and I think it's good for their stomach to have something in it if they're a little stressed about trailering. I think I heard someone say that it was a 5hr drive, so you might want to stop at a rest stop after about 3 hours or so and let him out to stretch his legs, get a drink, graze a little bit and pee and stuff like that. Now if you don't think he'll load back up, then of course don't do that. ;o)
After you get him there, just turn him in the round pen and let him settle in and get used to the place. After he's settled, walk him around and let him check it out but be careful coz he might still be so hyped about being in a new place that he'll run over you. You might want to carry a small crop or something to get his attention, just in case. Like everybody else said, ride him in the round pen first, then on short trips. Work the confidence level up for both of you and you should have a great time! Enjoy!
I was the one who said it was a 5 hour drive. It might be more for her. She lives North of me, and I don't remember how far South she is going. I do not agree, with letting her horse out, at a rest stop. It's a holiday weekend, and the roads and rest stops will be jammed. If he got scared and got away from them. It could turn into a real mess. She could, and should stop and let him rest, while in the trailer. Ours would pee in the trailer, but didn't want water. We always kept a hay bag in front of them also.