Be sure you have him take things to secure the awnings that I see loose now. They are nasty when they get open on the road, and are very expensive to repair or replace. They may be just fine, and only need to be rolled up properly, but don't tow without that done.
As said above the 12 volt
power for the running lights, signals and brakes come from the tow vehicle, so he needs to be able to get all of that operating right. I see an electric tongue jack, so that will also need 12 volt
power. He probably should take a new 12 volt
battery for the trailer with him, available at any wal mart. That will power the jack and the break away switch on the trailer, both needed to move it and be legal.
Everyone is going to tell you to buy new tires to move it. I will agree in advance. Too much damage can occur with a blown out tire to chance it.
I hope it either comes with, or you have a Weight Distributing hitch for the trip.
Welcome to the shiny metal madness group.