Not only is this a good idea in its own right, but I think that 1KChinito is also alluding to the fact that there's a decent, though not guaranteed, chance that both of you will be seen together if you show up at the first of the two appointments.

There's one important thing to remember, though, since it sounds like you might choose to wait a while to schedule your interviews. Be sure to use the online system to schedule interview appointments, whether or not you plan to go to them, within 30 (or is it 60?) days of when you receive your pre-approval notice. I might be wrong about the length of time, but if you do not make appointments within a certain period of time after you receive your pre-approval notices, then your applications will be canceled, and both of you will have to start the entire application process all over again. The 30 (60?) days does not apply to the interview date itself, but to using the online system to schedule a date for the interview. It can be anywhere at anytime; just reschedule it when you have a better idea of where and when you want to do your interviews.