Well I don't know where you are at or what the weather is out there.
Is it all day long? Does your trailer have a water container? If it does I would bring a bucket and let the horse drink after cooling down from the ride.
If it is raining I would bring a sheet to put over the saddle if you do take breaks (make sure your horse is okay with it though!). It is nice to get back up into a nice dry saddle
If you do ride all day I would stop and take a break if the horses get winded or every two hours or so. If you don't take a break I would get off and walk for some time and get back on (this can be dangerous but I went on a Oregon trail reenactment for a week and getting off and walking your horse for a good couple of miles helped the horse out a lot). But then again its all on how phisicly capable your horse is.
I personally don't graze my horses, especially on trail rides. When horses graze and they are not used to being in a certain area they (from experience) tend to get a little spooky when eating. They also get some bad ideas and think they can get away with sneaking a bite or two (which can get very annoying if you don't like your horse diving into plants). I don't know what he vegetation is like over in North Carolina but toxic plants are always on my mind wherever I go. I had a friend who would graze her horse on trail rides, but he ended up passing away sadly from eating something toxic on his last ride.
When taking breaks I like to loosen the girth of the saddle. That is a personal opinion, but remember to tighten it when you get back on! (I like to swing a stirrup up and keep it in that position so it will remind me to check the girth again when I get back on).
I wouldn't take tack off until I get back to the trailer. I also like to brush my horse off after any ride. This helps him not to feel as itchy. (If there is a nice sandy dirty spot I also like to take my horse over to it to offer him to roll. But be careful of the lead! Getting a horse tangled up isn't fun, or dropping it and having the horse take off running isn't fun either haha). I also like my horse to be dry before I load him up. My trailer is open and we don't get very warm air around here so the worrysome me always have the thought of 'Is he shivvering? Is he cold? Is he to warm?' come though my head haha.
Here is a hint of wisdom. Keep your cell phone and a water bottle on yourself. Not on your saddle. If you fall off and your horse takes off with your personal items on the saddle.... you can be stuck for a very long time.
Sorry for the long post... but trail riding is what I love haha. Are you spending the night out there? Or is it just a day trip?