Just let people who already know the things you are teaching miss the class entirely. Give them some test at the end, this is okay but do not force them to suffer the endless hours of something they are already good at just because you want them to attend.

My CS professor and web dev class professor don't require attendance in class. These are two classes where you can honestly learn it on your own. Despite having a 102 in the web dev class, I'm still present in every class. If nothing else, I work on the projects we have, since it's an 75 minutes in front of a dual screen PC. (Plus we have VS on these computers, and I quite like it.)

In my university we have two evaluation paths: Continuous evaluation, which forces you to attend the lectures, do some (usually) partial exams, and deliver the projects during the semester, and Final evaluation, which has no attendance requirement, but has only one final exam, and the project delivery is at the end.
This way we can choose between knowing our progress along the curse, or not going to classes if we cannot attend them, or would rather not to.