I have done this for many years. There were really no cons. Had excellent attendance, in the many years I've done this, only one student did not show due to religious issues. Audience attendance was so high that it became a regular tradition that they audience loved.
Major pro is that I never had a concert compete against a basketball game or against other extra curriculars and we were able to do concerts for both MS and HS on the same day. To me one Sunday afternoon is worth two late nights on the week that you would probably be having to have the same concerts separately for MS and HS.