I use two
Simplicam WiFi cameras to monitor my park model. These cameras do need a fast WiFi source which might be a deal killer for a campground.
Very easy to set up and maintain. My park model has lost power a couple of times and the cameras come right back online.
Each camera is $150. I have 24-hour recording on each camera for $5 month per camera. That allows you to review "events" like noises or movement.
You can set up each camera to email you (or smartphone message) when an event is triggered.
Simplicams have 2-way audio so you can hear and talk to whoever is near a camera.
Cameras can be monitored via computer or a smartphone app.