I bring a 12 volt battery camping, 35 amp hours with 4 cigarette plugs available (30amp fuse on the main, 10 amps for each plug) in a marine battery case. I can power phone chargers, a laptop (using a 12 volt power cord, pretty efficient), fans, a bug zapper, and even an electric blanket (4 amps per hour, but auto-off after 30 minutes so it's only a 2 amp draw). I also have a quality 800/1600 watt inverter which can power most things I may bring except power tools (works great for charging power tool batteries).
Yeah, it isn't hardcore camping, but I camp a lot (30+ nights per year), and with my kids (4 years old this year).
This is probably overkill for your use case (for most everyone). But, it wouldn't be difficult to setup a smaller battery in the 5 to 7 amp hour range (5 pounds of battery). It would be far more portable and more than enough to charge a couple of phones for a three day weekend.
You can also get a lightweight, foldable solar charger, here's one on Amazon with 2 USB ports for $70:
http://www.amazon.com/Foldable...
Just some ideas, there are plenty of ways to apply technology to power our technology when in remote locations. If only cell service was available everywhere...