I 100% agree with Mike.
From your post it appears you feel some sort of obligation or guilt about making the best decision for your business which you actually
already made when DCM declined the extra days and you offered those days to others.... DCM did not feel obligation or guilt when she reduced to part time. If her ds's childcare was a
need (for her to be able to work) she should have protected that...
This behavior on the parents part actually surprises me when I read it on here because my own dd's preschool parents would not even dare ask they would know the "center" would not hold or have spots after their maternity leave so parents would not even dare ask.... maybe because we are home based providers, parents expect us to be "emotional" and "sensitive" to their pregnancy, their budget, etc. and put our own business aside for their life.
You are doing the right thing....