From a campground perspective, the bandwidth being halved is not that big a thing to me, the benefits far outweigh it.
1) you would never get 802.11N speeds on the internet side of any campground and likely will never see 802.11G speeds either so only getting 27mbps is probably going to be far more than you need anyway
2) from a security perspective, using a repeater/router setup is the single most important thing you can do in a campground as it isolates you from most types of attacks and security breaches that could take place on the "public" campground network (although some radio solutions also use a router, but not all)
3) the Linksys WRT54G is also a tank, it is well overpowered for what it is doing and you can also run it off DC as it will tolerate 5-24DCV, so just cut the wall wart off the cable and put a cigarette lighter plug on it and it runs off your house batteries
I have also noticed that most of the campgrounds that we were in this summer are starting to realize that they need to build their WIFI network properly and are using directional long range antennas to get back to the office as opposed to repeating the signal, so you get the full strength in the back of the park. This means you only need to repeat once (on your router).
Rob
rvtechwithrvrob.com