an advantage of buying two different ones is that you each may decide you like the other ones reader better, and you can then swap.
ereaders vary so much that a lot of the choice really just boils down to personal preference. read through the threads here to see how passionate some folks are over touch screen, no touch screen, etc.
my best recommendation is to get a hands on preview before you buy, or maybe narrow it down to 2 or 3 and do an in home trial. getting it right would be worth return shipping.
as far as the library books on the kindle, i would say that your ability to get on to this forum and post a message demonstrates that you have the requisite skill set for getting library books onto your kindle. setting it up requires downloading and installing software. once set up, it is a very easy process.