We just ask the reception at the campsite were staying if its possible to charge our phone's and they havn't refused us yet, in any campsite everywhere we've been. Because we use double AA batteries on everything else, night (head lamps), rear lights and camera, we cary along a (lightweight fast loading) battery charger and none have a problem with that either. Sometimes we just ask the trailer or mobile home next to us, this is also a good way to meet people, and after meeting us they also watch our stuff when we go sightseeing or shoping.
We do offcoarce offer a beer