Hi
I would think that yours, mothers and uncles birth certificates would be enough since yours proves that you are the child of your mother and your mothers and uncles would prove that they have the same parents and so that would prove that he is your uncle. I would think that your parents marriage is completely unrelated. Immigration in Canada will not care who your father is or if he was married to your mother. At least I cannot imagine why they would. Is your uncle saying that immigration wants to see this document? Maybe he is just curious to see it himself :)
Marriage certificate to show the name change of the mother. As the birth certificate would show the maiden name of the mother, while the OP would be applying with his mother's married name.
PMM