Opening the book…
People decide how much truth to give you based on whether you seem to see them as a person or a function. Asking for effort before you have shown any interest reads as extraction, and it sets the price of future requests higher. The information also has practical value: you cannot tell when someone is struggling if you never knew what normal looked like for them.
In your first week, work through the roster deliberately — names, pronunciations, and one real detail each: a kid's football club, a night class, a sick parent, a band. Write them down if your memory is unreliable; nobody is offended by notes, everybody is offended by being called the wrong name in month four. Then reference the detail once, later, without making a performance of it.
In a genuine emergency you ask for the work first and learn the names afterward. And with very large groups, this applies to the people you deal with directly — faking intimacy at scale is worse than admitting the limit.