Change pretty well said what I was thinking. Since you mentioned having to borrow a trailer from the barn, go over it with a fine toothed comb. If it has the wooden floor, look up under it and check the bottom of the floor boards for discoloration, which may indicate rot, which a 1000# horse could fall through. Same thing if it's a metal floor, check for rust areas, again indicating rot of the metal.
Yeah, it's kinda hard to pull a 3 or 4 thousand pound trailer with a Honda, let alone loaded with a couple thousand pounds of horses.
I looked at the website for the ranch ya'll want to visit, looks fantastic. I say go, have fun, and enjoy the family time
Good luck with everything,
The silent communication with horses. A trust that can't be bought, earned, or convinced, you are either their kind or your not..