I think it is important to point out the 30 amp legs you draw from must be totally different from one another. The second one coming from another site's connection box. This exposes your scheme and as you pointed out you better check with park management for permission. I'm no expert here, but this is how I understand it.
It's amazing how many parks will not go 50 amp even on new installations. They are in the business of selling electrical hookups as well as park space. They can add $ for the 50 amp use and increase the parks ability to service a larger clientel base.