Thanks for the information.
The disconnect at the meter is the main in this situation.
The first stop from the meter is the the main power disconnect per code.
Anything after that, is considered a sub panel.
In your case it is a pedestal, but still a sub panel and it provides power to the receptacles through the breakers in the pedestal.
You are required to run 4 wires from a main to any sub.
There should be a ground rod at the meter/disconnect and a ground lug already for connection of the ground wire to the pedestal.
You will also need another rod at the pedestal location to connect to the ground bar along with the ground wire from the main disconnect.
So, you need 4 wires.
3- 4/0 cables and one #2 for ground
Table 250.66 has #2 for ground with use of 4/0 power cables
For pedestals on RV's, the neutral is sized the same as the power conductors. There is no reduction unless permanently connected as shown below:
551.72 Distribution System
Receptacles rated at 50 amperes shall be supplied from a
branch circuit of the voltage class and rating of the receptacle.
Other recreational vehicle sites with 125-volt, 20- and
30-ampere receptacles shall be permitted to be derived from
any grounded distribution system that supplies 120-volt single-
phase power. The neutral conductors shall not be reduced
in size below the size of the ungrounded conductors
for the site distribution.
The neutral conductors shall be permitted
to be reduced in size below the minimum required
size of the ungrounded conductors for 240-volt, line-to-line,
permanently connected loads only.
Just reply for any other info or clarifications.