You know what your wife likes? Load up some apps, games, books, and other stuff that will appeal to her. Hand the iPad to her, then start saving for your own.
Anyway, on the road it will run for up to 10 hours without a charge. Not even your Macbook Pro is that good.
Instant on, so it's good for looking stuff up when starting the laptop is too much bother.
Easy to cary around and use in different rooms.
An app for almost everything, and they are absurdly cheap compared to buying programs for your computer.
Books, and not just one book store like the Kindle, but almost all the online ebook stores. And a lot nicer to curl up and read with than a laptop.
Instantly, always ready to use. That really can't be overemphasized. It changes your whole attitude to the internet. And while that is true on the iPhone, who really wants to browse, read, view a map, or almost anything on the little screen if a bigger one is within arms reach and just a quick to use?
And finally, the most important argument of all. It will make her geek husband so happy he will even take out the garbage without complaints or reminders.