Take a look at Indian Point in Gautier, MS. Very nice park with access to Sue Bayou if you have a boat and like to fish. Had a buddy that stayed there for a few years and they loved it. The entrance is gated and manned 24/7 which can be a plus or not, depending on what you want. Big spaces from what I could see with room in between your neighbors.
Just a word of warning, though. The entire park was underwater during Katrina, as was most of the Gulf Coast. If you won't be able to evacuate with your trailer I'd look for something north of I-10 but not to close to the Pascagoula River delta.
Getting to Pascagoula from Gautier is very easy and quick using Hwy 90.
