How do I keep my Group X program from getting bullied by my members?

I am a group exercise director. My small club has 6am classes 5 days a week. Truth be told they are spoiled and don't need 5 days a week. They should only really have 3-4 days a week. There is one instructor they like who teaches Tuesday/Thursday 6am. She also teaches Monday/Friday noon and Monday/Tuesday/Thursday evening. My Friday 6am spin class has opened up and I have given it to a VERY qualified, awesome instructor who I highly respect. My members don't want her because they want the popular instructor. I know that I need variety in my programming. Plus, the popular instructor is also a personal trainer and needs to have some availability to book clients in that time. Also, if I don't have a variety of instructors I will never be able to find subs when I need some. How can I educate my members (who are trying to hide in anonymity) that if they give this great instructor a chance they can get a great workout? They don't need only this popular instructor.