I agree with Bill that this is one of the more stupid "technical" handouts I have ever seen at a campground. There are so many inaccuracies in it that it's not worth dealing with point by point. The use of your Jetpack is not going to affect other people's ability to connect to the wifi even if you are both using the same channel. Furthermore, it is simply wrong to say that personal routers emit a "potentially harmful unsecured signal" since almost all routers these days use the same or better security than the campground's wifi does.
My reaction would be to ignore it particularly if you're only spending a night or two there. They would have to be able to prove you are the source of any signal they detect which is easier said than done. Unless your SSID is your name, they would have to map out signal strength at the CG to prove you are the culprit.
Personally, if my choice was using my 4G hotspot or a crappy CG wifi, I'd leave before being forced to use the wifi.