I have this problem, you see...

I might recommend not using a printed questionaire for this, or doing the verbal equivalent. I think that your idea of going in with a list of questions that you'd like to know people's responses to is a good idea. I expect the answers to be less useful that you might hope.

When I was serving my time as a high-priced consultant, universally the best way to get honest responses that match observed reality was with face to face verbal communication. This type of communication also provides you with a prime opportunity to get your point across, just by asking the right questions.

Bringing a printed questionaire into this creates a gigantic barrier to open communication, especially because people think differently when writing and when speaking. Make sure you're indicating in your non verbal communication how important what they have to say is, as well. Don't have much more than a piece of paper for taking notes in front of you, and don't spend too much time looking at that paper. Look at them when they're speaking, and you'll be surprised how much useful information flows.