congratulations on teaching such a successful and popular class.
You know well enough that class participants are often reluctant to change because they are in their comfort zone. Depending on the nature of the change, you can always ‘sneak’ it in and teach the rest as you have before.
If the changes are more fundamental in nature (a class of less intensity to reach different students, for example) then you could give it a snazzy name and capitalize on the popularity of your class; for example “The softer side of Maurice”.
And if that does not work you can still go back to the original and successful format.
It’s working for a reason
Why do you want to change it?
What do you wish to accomplish with the change
Whenever I got bored teaching I would add a longer warm up or cool down or use more or less step or more or less resistance modalities.
Think about possibly adding duration to certain segments one week then add intensity the next.