exam combination

This is never a question that a tutor can possibly give an accurate answer to for any individual student that they have not had direct teaching contact with - certainly 2.5 months is definitely adequate time to prepare for 2 exams, but it will then be a question of how much study time is put in by the student and how competent that individual student happens to be! I would suggest start with one subject and see how that progresses over a 2-3 week period before deciding whether to pick up the 2nd subject.