What would the purpose be of the trial month if it didn't mean you could get the last months fees returned? If the last month's fees were not returned during that trial month then it would just be a matter of terminating care and using the final months payment as weeks of notice (which would not be a trial month).
I feel like legally you are not allowed to demand last months fees for home child care. I thought CRA was rather strict on how things are called and your deposit needed to be very carefully worded (same as holiday pay) otherwise you put yourself into a different form of employment (not self employed). Hopefully others can clarify this.