Your survey questions require students to be thoughtful and introspective. Have you been successful in getting them to do that? If so, how? Most of us have been frustrated by their proactive participation.
You seem to have a different application of secret shoppers. I'm most familiar with the concept in the admissions process. You seem to be suggesting that you have "shoppers" actually assume the role of enrolled students. Is that correct and how do you pull it off?