iOS 11.3 will have implemented by the Apple company a new very useful function for Face ID, those from Cupertino fulfilling a request of parents who have children with iDevices. They asked for the possibility to use Face ID to authorize children's payments, and the Apple company implements this functionality only in iOS 11.3.
In the video clip below you can see how Face ID allows the authorization of payments made by children who will have iDevices with iOS 11.3 logged in to the same Apple ID as their parents. When Touch ID existed, Apple allowed fingerprint scanning to authorize children's payments, but this functionality was not implemented for iPhone X and Face ID.
iOS 11.3 still requires parents to enter their Apple ID password to authorize the first payment made using iPhone X, but the option to enable Face ID appears for activation. After it is activated, this function will always be used in iOS 11.3 so that parents can authorize payments for children who have iDevices.
