Can you ask the instructor(s) which would be best suited for you? You seem to have a good idea of what you want to achieve and are honest with your current abilities. They can help direct you to the class which would best benefit you.
If the classes aren't specified "beginner" or "advanced", most instructors should be able to accommodate a beginner in their class. Let them know you are new to yoga, any restrictions or health concerns you might have, and your goals.
If I was a beginner and did not receive any direction from the instructors on which class to take, I would too start with Iyengar. GL!