All the points about biometrics having lower pass rates for seniors and kids are valid. But the solution is not to ban them—and in effect anyone traveling with them—from using the program gates, but to do it with that understanding and have a backup system in in place. Eg for US Global Entry people of all ages are eligible and the system uses facial recognition, no longer relying on fingerprints or even needing to scan your passport. This speeds up the process considerably. But for people of any age for whom the system is unable to get a match, they are sent to a counter for a human officer to perform the task—just like they are today, but as a backup, not the primary method.