You can use three of your 10 days for personal business, provided that the days are approved by your principal. Personal business is officially defined as something that cannot be done at any time other than a school day, during school hours.
Reasonable notice must be given for personal business that is scheduled in advance, such as the closing on a house. This allows you an opportunity to speak to your chapter leader if you feel the principal is being unreasonable in denying your request. If you are out to take care of a suddenly ill child, advance notice is not ordinarily required. Personal days are part of the contractual right to 10 self-treated CAR days allowed each year, not in addition to those days.