Is there a way to set up Ubuntu 12.04 (or earlier versions) so that all recommended updates are done automatically, say once a week? When I say automatically, I mean no password entry or user intervention required.

This sounds like a stupid request, so let me tell why I'm asking. My grandfather knows nothing about computers; he uses his solely to read Yahoo! mail. I want to get rid of his clunky, spyware-ridden Windows XP and install Ubuntu. I want to set it up so when he turns the computer on, after a couple minutes, voila!, Yahoo! mail, already signed in, ready to go. The problem is I don't want to have to go over there every week or so and make sure everything is up-to-date, he hasn't accidentally installed any spyware, etc.

So can this be done? Is this the best way to set things up for my grandfather? Are there other things I should be worried about when it comes to keeping things hassle-free for him?

Please don't post anything like "why not teach him how to... blah blah blah". My grandfather is 80 years old and has made it clear email is the only thing he will ever use a computer for!

Thanks!