Good for you, I spoke with two teachers today who have a similar schedule and they agree.
Pranayama at the end of your practice is also a benefit over doing it before. At Sivananda we follow Swami Vishnu-Devanada's instructions to do pranayama after other asanas also as one is more open after the asanas. I know a lot of classes do it (if they even do) before asanas.
You are wise to scale down in the method you have chosen as the sudden shock could be unnerving. It will give your students greater opportunity for independence and allow them to gain more depth....watch and see.