We use Verizon with our Jetpack. We also stayed in the boonies in the West and we got good service. If you're traveling West, Verizon is the one to get. East - don't know. However, definitely don't rely on campground Wifi. It's awful and they don't usually let you do streaming. It's purpose if for email and short surfing.
As far as towing a car. It's simple. You pull to your campground site area, disconnect the towed and park it in a empty site or wherever. Back your RV in and park the towed at your site. If the park is small you can also unhook the car at the park entrance, drive and park at your site and walk back to get the car. You can also ask for a pull-through spot and no unhooking until you're parked. It really is not any bother. Just don't think you back your RV with the towed vehicle attached. You can't and shouldn't try. A foot or so, yes, but no further.