I am going away for the full Pesach, but my family will be staying at home. Can I just lock up my individual bedroom (and instead of cleaning a room that would not even be walked into, spend the time helping my mother with the rest of the house)?
Locking the room is not sufficient on its own, but you may sell the Chometz in that room in a Mechiras Chometz.
The Mechiras Chometz involves also renting the area over Pesach. Therefore, this room should not be accessed by others throughout Pesach.