I see the cables say they're for a mobile device, but they'll fit my Macbook Pro?
For your purposes it makes no difference. They're referring to the fact that mobile devices have the 1/8" miniplug audio output. But -- so does your MBP.
McGiord suggested optical (because your MBP does have the ability to push optical audio out the headphone port) and that would be cool, but you ought to be able to get away with regular analog.
The people pushing ATV have a point if you're wanting to set up a permanent video link so you can watch stuff anytime. You didn't say you were, and I figured you weren't, but if you are then you might want to explore that kind of solution.