Now, The Rasberry Pi offers an opportunity to learn something new-- to create,to wonder,to ponder, to make mistakes,to try again, and to perhaps even succeed....a chance to work the old grey matter a bit ....all without the worry and expense of losing files or messing up a Granny"s very expensive laptop! To hang with being very very careful ....the Pi is pure Magic!! Brilliant !!
No.1 son ( like Eben..grownup and very very busy ) will guide the plugging- in-where stuff and then we are on our own he says
No.1 son is very useful ...he does find time in his busy life to keep Granny"s laptop updated and humming along... Bless his pointed head
If you look at this link: http://www.debian.org/CD/live/
you can download a so-called 'Live CD'-file of Debian Linux. This file is burned to a CD or DVD and once completed makes it possible to run Linux from the CD on almost every computer without changing anything on that computer. So when you used it and shut off the power anything you did vaporizes into oblivion.
I'm sure your son can help you set it up so you can get a taste of what the Pi will do when you get it. It will make it easier to ask the right questions.