I would be inclined to speak with the parent and let them know that given that expenses have gone up since you started caring for the children that you can no longer give the subsidized rates. Even if you allow it for the Christmas break use that as their final time. Let them know that you will be raising the rates as of January for the afterschool child to the full day rate for non school days as a starter. That will cover March break and summer. Expect them to find a teen for the summer but that is ok too since by then you will be ready to replace them with two full paying clients.