None of the above! I let parents know far in advance when I am closed and if they are not able to book the day off it is their responsibility to find alternate care for their child. As Playfelt stated, I am full so can't be anybody's backup.

If you kept a space empty at all times and allow dropin care then that's your choice but you're losing out on income to do somebody a favour once in a while. It's up to you and what's best for your family.