Just make sure if you use a rack on the back of the trailer it is not the kind that folds down. The back of a trailer bounces more than the back of a car or truck so that hinge can brake. Yakima makes a rack designed for this with a solid elbow connection. It is a 4 bike rack and we usually carry 3 bikes so it works well. Haven't had any issues.
I researched the idea of a front hitch, but already had a hitch on the back of the trailer, so that made more sense. I liked the idea of having them up front, but lots of people complain of dirt, bugs, etc when on the front. You also would not be able to put a cover on them due to not being able to see through the cover and no headlights at night.
We were following a 5th wheel the other day and his bikes were mounted more to the right side, with the cover I could not see his right tail light. It turns out his left tail light was out so he essentially had no tail lights in the back. I wanted to tell him, but we pulled over before he did. Hope someone told him before he got to far, this was in MT and he had CA plates.