It is going to be cold tomorrow where I am. Not too sure about your weather conditions, but if it is going to be cold or even a bit cool you probably want to make sure that your horse is not standing sideways and has protection such as a tarp over the front of the trailer so that he does not get sick.
What kind of trailer? How is the weather where you are? Has your horse trailered before? How far are you going?
If I'm going to a show or a trail ride within 100 miles, I don't do anything but put him in the trailer. Unless he is a real problem, or a very tall horse in a very small trailer, or it's very very cold and you need to go a long distance, then you really don't need to do more then what you've done.
There are all sorts of things people do for horses but I've usually found that it's really done more for them then their horse. I've been trailering horses for ~30 years and never had a problem aside from a bump on the leg or so. Nothing that ever caused me not to ride when I got where I was going or to need care when I got home. I've had more bumps and scrapes at show or the trail then I've had trailering.
All I have ever done for my mare is put shipping boots on her. If you have an open stock trailer and its cold a blanket may be in order, but otherwise the horse should be just fine. Unless you have a problem horse, it really is a simple matter.
Most horses are okay with little to no protection. I prefer my horse to wear float boots, a tail wrap and a rug, just to be safe and make sure she doesn't get any cuts or scrapes, and also to make sure her tail doesn't get tangled or rubbed. If it's your horse's first time in a trailer, they might be a little nervous, but what you've prepared shoul be fine. You might want to consider a rug if it is cold, but also to protect from little cuts. Some horses also wear fly masks in trailers, to protect their eyes from dust, you might want to consider that too, although it's definately not a must.
Eep I wouldn't put a fly mask on my horse in a trailer... At least not the enclosed ones we have here in Aus, it's already dark in there and a fly mask impairs their vision even more.
A lot fo things depend on the type of trailer you're using... in my trailer I have to make sure that I tie my pony up tight enough, otherwise he can turn his head and get it behind the pole that the head divider hooks on, which is super dangerous if we have to hit the brakes!
The only thing I ever put on my horse in the float is a cotton sheet if it's cold. If my horse rubs his tail then maybe a tail wrap. The only time I bandage is when i float with a friends horse who kicks under the rubber divider, if i don't bandage my pony's leg gets all cut up.
I think your pony will be fine with what you have :]