I use WiFi Ranger. But...
Don't expect miracles. The problem my not be the bars of signal you get. Two or three on a device is usually fine. One bar is frequently enough for email or slow loading of an Amazon or Ebay page. The campground usually has one connection coming in and it has a max bandwidth limit. Let's say it's a gigabit connection. So you now send it out to 4 or 5 locations through the campground. Each connection is a gigabit connection but it gets bottled up at the campground connection to the cloud (No one understands the cloud
). If you have 20 campers connecting to the Internet WiFi and streaming Netflix or Pandora a gigabit split 20 ways is about 50 megabits per connection. That's not even considered highspeed at that point. And how many campers are actually connected may be significantly higher.
The second issue is latency. To make it understandable, from your device to the bath house is a hop. From the bath house to the campground switch is a hop. From the switch to the CO is a hop. From the CO to the backbone is a hop. Every time you had a hop a packet of info is addressed and passed on. Think of it has mail going from post office to post office till it gets to your house. The more hops, the more time is added while a new envelope is created, addressed and sent down the line. This latency can cause a fast connection seem slow as the device must buffer the packets into place to build up enough information to run through decompression if its used.
In other words. You may spend $$$ for a wifi extender and still have unusable wifi, especially in a crowded campground on a weekend. I'd spend the money on a T-Mobile MiFi device where you get lots of bandwidth unrestricted (21 gigs starting 9/6/2016 or more if the towers are not congested) and unlimited streaming for supported services. If you're concerned about the lower coverage area, verizon hits a lot of areas that T-Mobile doesn't but be careful as HD video will eat up to 5 gigs of data in a few hours and it's typically possible for it to be more expensive depending on your plan. Make sure you throttle all your devices to use only low bandwidth data streaming for Verizon/AT&T.
I only have the WiFi ranger because my wife works from our camper on weekday camping and the about 50% of the time we can use WiFi to keep mobile costs down.
(Former Microsoft Server and TCP/IP Certified Network Engineer)
((That means geek))