I know, i have gone through this exact process myself, it has not been easy. The way it went for me is that my wife and i went there, they took us to a small room with two chairs and a desk, a glass window in between, on the other side was some cic/cbsa official, he asked a couple questions then told us he needed to give me a removal order because i had overstayed and was out of status, i told him i just applied for inland sponsorship but he said it didnt matter. I was given a exlusion order for a year and told to report to the CBSA office around the corner. There they took care of the arrangements for my departure. They gave me 2 months before i had to leave, told me to get a plane ticket and then let me go.
I dont think its possible to get legal aid for an immigration appointment like this but you can call them and see what they say. Also dont bring too much family, there is limited space in those little rooms. I dont know how long you have been out of status, but try to ask them for a voluntary departure order so you can come back any time after you have to leave Canada.