I would run from the panel 8 gauge all the way to where you plan on having the RV sit.
Run it all under ground encased in PVC.
Where the RV sits put in a 4x4 post, set it so it is about waist high and then pour some concrete into the base so it won't go anywhere. Then mount your weather proof box to it.
This way there is just a circuit for the Rv and nothing else and you don't have to worry about extension cords in the way of anything.
It's easy to do. Took me about a day to do mine at our old house and it was about 75' run.
I'm very picky about how work is done so it took me longer.
