I agree that the regular customers must come first. I think you should increase the rate a lot for holiday only cleans.
After the cleaning, if they want to be a regular, then the regular rate should apply.
But absolutely charge more for the first time and even more for a probable once only or 1/year.
I find that I usually keep 30% of the holiday customers for regular cleaning. But that first time always costs more.
Hugs,
Texas Girl