Your child made those purchases. You should pay the charges and use the experience to teach a valuable lesson to your child. You have already made sure a block was added to the line to prevent it from happening again. You should also look at your options in the Play Store to make sure you are notified if they try to make another purchase.
I'm most definitely NOT a VZW employee. If a post answered your question, please mark it as the answer.
This isn't much different than if she took change and bought a soda from a vending machine. You received a product that is non returnable. Verizon isn't liable for those charges. You could ask the maker of that app if they could refund it from Google Play directly.