Family Sharing is a new resource provided by Apple, where up to six people in your family can share purchases from iTunes, iBooks, and the App Store. They purchases can be paid using the same credit card, and the kids' spending approved right from a parent's device.
The PlayKids subscription is part of the restrictions that can not be shared through Family Sharing because it is a purchase within the app and you can download the app for free.
After the application is all released, follow steps 2 and 3 again to change the Apple ID to that of the person using the device.
For additional information about this, access this link from Apple Support: support.apple.com/HT201060