Tell your dad that he doesn't need 4" of lift for 35s. Best advice I can give you is short and straight. If you or he doesn't want to read up on all the info out there about lift options, simply do a 2.5 coil lift with 35s and be done. If you want to learn a lot more about the JK platform, read up here and ask mucho questions.
Tell em congrats on the new rig from us.