iOS will have new APIs for getting the age of a user. Sarah Perez writing at TechCrunch:

It puts Apple in the position of collecting kids’ ages via parental input but still puts the onus on the third-party developer to extract and use this information to craft age-appropriate experiences in their own apps.

Seems helpful to me. It doesn’t appear to address the flip side of age verification, making sure someone is an adult, but Apple could add that later.