This is the maximum number of children this room can accommodate.
A booking cannot be made for this room including more than this number of children.
If you set this to Dont Ask on all rooms the booking page will ask for the number of guests instead of adults and children.
If any room in the property allows children, the children selector will be shown on the booking form.
If you set this to None the room will not be bookable if the number of children in the booking is greater than zero.