Your dad cannot provide any flight training without a category and class on his flight instructor certificate. He will need to take a practical test to add the category and class onto his flight instructor certificate for the airplane you want training in.
§ 61.195 Flight instructor limitations and qualifications.
A person who holds a flight instructor certificate is subject to the following limitations:
(a) Hours of training. In any 24-consecutive-hour period, a flight instructor may not conduct more than 8 hours of flight training.
(b) Aircraft ratings. Except as provided in paragraph (c) of this section, a flight instructor may not conduct flight training in any aircraft unless the flight instructor:
(1) Holds a flight instructor certificate with the applicable category and class rating;
(2) Holds a pilot certificate with the applicable category and class rating; and
(3) Meets the requirements of paragraph (e) of this section, if applicable.
It is also true for training in a simulator, FSTD or other such devices.