Do you plan to travel by train around Switzerland? I would suggest to rent a car ( I understand that you are in 5) and go directly from Malpensa to Luzern (3h drive). You can spend your first night there and then head directly next day to Interlaken. You can spend 6,7 and 8 March there and then come back to Milan on 8 March evening. In this way you can relax on 9 March in Milan and be fresh before the flight.
http://www.myswitzerland.com/en/home.html