Google Play not only is the largest app store in the world but also a music subscription service, a bookstore, and a video store. Google Play gift card make an excellent gift (hence the name), but that's not the limit of their use. Since Google restricts underage users from Google Wallet, Google Play gift cards are the only way for your munchkins to purchase content. Here's where to find them and how to use them.
Google Play gift cards are available in brick and mortar stores in a plethora of countries. Here in the United States, they are available at Target, Walmart, Wallgreens, CVS, GameStop, and a host of others you can find right here. If you're looking to add to your balance without leaving home, you can purchase Google Play credit directly in the app or on the website. Both gift cards and credit come in set increments, starting at 5 dollars for credit and 10 dollars for physical gift cards.
Redeeming a gift card for Google Play is a simple affair: each card comes with a code on the back. Scratch off the silver covering, and enter the code by tapping "redeem," either in the navigational drawer of the Play Store or within the payment options in your current purchase.
Once you've inputted your code, you'll be asked if you're sure this is the account you want to put it on.
Once you accept that this is indeed the intended account, the card's amount is added to your balance as Google Play credit. That's all there is to it.
As a small reminder, Google Play gift cards nor Google Play credit cannot be used towards physical items like devices and accessories; they are only available for digital purchases of digital goods. While we wish that you could send Google Play gift cards through an email, which other major online stores like iTunes and Amazon have allowed practically since their inception, anything that lets us avoid directly putting our credit card into our kids' IAP-riddled accounts is welcomed.