If you usually teach 15 and have to teach 40, then that is a large class. If you usually teach 70 and have to teach 120, that is a large class. Have clear guidelines and procedures for attendance, participation, make-up tests, late assignments, etc. Include rationales for these rules. When handing out papers, give them to the front row to pass back through the audience.
Students can put in and retrieve assignments daily at the beginning or end of class.
This gives fast and accurate feedback. To keep in touch with students, use email. It is an efficient way to communicate with students, and one to which students pay attention. To keep order, enforce strict discipline about chattering during lecture. Explain this on the first day of class, with a talk about mutual respect and civility.