I recently upgraded my wife's phone and gave the old one to our daughter to play with. I want an app that she can use to text and make calls from while on wifi network. I know there are some that do one and not the other but I want one that does both. Also needs to be free as my daughter is only 10 years old. Thanks
Since you are on Sprint than I would definitely say Google Voice is the winner here. Sprint has partnered with Google to make integration easier, though if you want all devices to receive voice calls (laptop, tablet, etc.) than you have to deal with certain quirks.
Also Sprint allows you to use your main number as your Google Voice number so you can have people call just one number... Plus using Google Voice on Sprint is completely free outside of your regular service charges for your phone.