I am not new to gardening in the northeast, but no longer have a yard. I recently relocated from Boston to Queens. My apartment came with a 500 squarefoot north facing terrace. I have no clue what to do with the space, I would like to have some sort of plants out there year round. What type of containers should I use? I live on the 2nd floor and there is an elevator in the building. I have two children under the age of four, so I need plants that are not toxic. Any advice is greatly appreciated.