If you son vacates his pitch first you will only have to swing the caravan through approx 90 degrees to get the tow hitch facing the vacant pitch. Should be easy to hitch up and drive off from there.
I was advised by Alko that the only place to attach a rope to, other than the tow hitch is around yhe axel.
Then only with a "spreader" or "Y" strop so the pull is applied on the axle in two places where the chassis rails run. Most definitely not by a single attachment point on the axle!
One more thing I would like to add. If you had a mover fitted you would be able to do whatever you like with the caravan backwards or forwards, even swing it round 360 degrees. You would not have to worry about any of this fixing a towrope to the back of the chassis and as for a slope it would just take that in its stride..