Good campground near Jacksonville,FL

When you mention large rig/site, the one that pops into my mind is North Beach Camp Resort. A little pricey, but full hookups with cable. Cell reception is iffy in some areas though. But they have massive pull through sites. The ones closer to the ocean are more tree covered.

Closer in town is Kathryn Abbey Hanna park. Also full hookups, but call to make sure they can accommodate your rig.