Costco offers the best deal around on iTunes giftcards. You can get $60 worth of cards at a discount(I think it's maybe a couple of bucks) but, best of all, sometimes they have them on a real SALE... You can then get $60 of iTunes giftcards for a *big* discount, I think the last time I saved maybe $10?
FYI - The iPod (and its funding) can become a great reward-system for any kid

. Word to the wise - Be careful that your kid doesn't run up a lot of charges and start charging stuff on your credit card, keep your eye on what they're buying. That's why I like the iTunes giftcards.
I can pre-fund their account and the amount that is waiting on the account sits in that upper right-hand corner.
agnes!