Thanks for the advice, StuartO! Yeah, I think satellite will be too expensive and I'll just buy them a smartphone. It's going to be adventurous to teach them how to use the thing...;-) Three sounds good, since they're mostly planning to travel through France and Spain. But I'll have a look around and see if I can find a servive that does allow tethering. Will let you know if I find something.
I don't know too much about this, so sorry for the potentially stupid question, but is it possible to build website offline and upload them later on?