Campground sub panel grounding question

I’m involved in maintaining a small campground. Some areas are served by overhead electric and an underground services.
No ground wire was ever ran or pulled from the main breaker panels. Individual ground rods have put at each sub panel. And they are bonded in many cases. What we are doing now is putting in new sub panels on our utility poles and installing new 50/30/20 outlet panels for each RV site.
Each sub panel at the utility pole has a ground rod that’s for that sub panel. Do we run a ground wire ground from the sub panel to the new outlet panel or put another ground rod at the
new 50/30 /20 outlet panel? It would be impossible to run a separate ground wire in the underground conduit.

Edit:

The conduit is PVC. With 3 wires 2 hot one neutral. No ground. Overhead is aluminum triplex.