I'd just have the person coming over to feed and top off to feed much less than you do. People who generally don't have their own tank as add more than you want them to. Your fish will be fine to be fed less over those two weeks than for the person to accidentally overfeed and you'll have more problems than just fatter fish.
For your media bags and media, any chance you can have your friend keep up the same change regiment you do? I don't necessarily like the thought of doubling up media as it doesn't really equate to lasting twice as long... more so it lasts the same amount of time but 2x more powerful! Or change up your media regiment when you are out of town and unable to monitor any potential side effects.
Just my 2 cents.
FWIW, when I used to travel, barring anything going wrong, I came back to a tank that looked nicer than the one that I kept putting my hands into.