A "dongle" is just the name used to describe a wireless modem that you plug into the USB port of your laptop.
It's works off of a 3G mobile phone signal instead of normal ADSL but is relatively quick.
You can plug in a web cam and take pictures with it using your laptop connected to a mobile (Movistar) modem. Obviously as you mention that there is no electricity in the area then your limitation is the battery life of your laptop.
So yes, you can do what you are saying, no problem.
One thing to note, most modern laptops now come with a camera installed so you could use that to take pictures if that's what you are trying to do.
Hope that helps.