I am in the mobile device business. It is very volatile right now in terms of changes.
Carriers are shuffling their spectrum and buying new as they prepare for higher speeds and new bands. This means a device sold last year or even now does not always support the latest bands and spectrum (example is TMO and 600MHz). That said I would highly suggest something very modular so you are not selling something that is limited 6mo from now. It also allows for upgrades later. This would apply to any modem or repeater preinstalled.
Carriers will continue to all move things around over the next few years as they prepare for 5g. Also know that as LAA (License Assisted Access with unlicensed spectrum) will become a big player as well to help boost speeds in the next year. How this all plays in campgrounds will depend on their coverage and locations but it will hit many popular ones.
WiFi ranger is a great solution for boosting wifi from what I have read but it is very pricy for what it does. I can build the same thing for litterally a third of the price with off the shelf components and about 10min all of which could be upgraded when they become obsolete.
I use this to connect to campground wifi.
https://www.amazon.com/dp/B003YIFHJY...=1GE7BHUGO66K8 note the removable antenna.
This for WiFi in and around the camper that I connect all my devices to
https://www.amazon.com/dp/B004ZF0I3U...=1GE7BHUGO66K8
If WiFi is far I use a directional antenna only when needed but you could use a high gain omni directional antenna in a more permanent mount like WiFi ranger does.
https://www.amazon.com/dp/B00P7Z9338...=1GE7BHUGO66K8
Cellular I use my personal WiFi hotspot or cellphone hotspot and connect to that to prevent having to swap all my devices between the WiFi networks.
This does not include a cellular booster but the whole setup is $170 compared to $500ish for WiFi ranger which provides the exact same functionality. Wifi ranger is expensive when most campground WiFi cannot support a single stream of digital content in many cases and it cannot overcome this limitation.
As far as rate limiting, campgrounds that do this also limit or charge per device that connects to the network from my experience so better to consolidate IMOP. If users want to break them off the trailer WiFi and connect direct to the campground they can. In the end you cannot speed up the campground connection and most have little more than home based high speed access. I have gigabit to my home so things are always faster at home and my kid notices.
My suggestion is to prewire jacks and power and include options with something like a cradlepoint modem or something like above that has a backup usb port and a screw on replacable WiFi antenna that can be upgraded to higher gain external. You could use campground WiFi, add a better high gain antenna, add a USB cellular modem or interact with a WiFi hotspot and not have to charge people who want to do it on their own or don't want it. Options with additional margin for FR with each check box I am sure.
Cellular Repeaters I would suggest after market solutions that plug in as options because they will change A LOT in the coming years and it would become either a PR problem and a production nightmare. Look for something that will support current bands as well as 600MHz and LAA.
Fyi the auto industry has tried this in the past and it took them so long to test (a few years of development) that they needed new solutions by the time they launched it. Maintainence is also a problem and when they shut off AMPs service they had to petition Congress to maintain it for a few more years to swap out the modems to digial.
If you have questions let me know as I am happy to help guide you through the Cellular side as I am very aware of cellular carrier band requirements and wireless technology movements in general.