I think that sort of thing has to go with how you feel and what you feel okay with.

The parents probably are getting paid for the day and took it as a sick or vacay day and will probably be reimbursed at their job.

However....if they are keeping little Johnny home to feel comfort on a difficult day then you may want to give them a break and it is a nice gesture to tell them that they don't owe for that day.

It is certainly within your rights to charge but it depends whether you feel right doing so.Also...is it just one day where they will be off or are they really having a hard time and going to keep little Johnny home for multiple days? Those are all factors