Why did Canada East and West decide to attend the Charlottetown Conference?

There is no such thing as Canada East or Canada West. Those are terms that were used in the 19th century to refer to the two regions of Canada that were united in 1867 to form the Dominion of Canada. The Charlottetown Conference was held in 1864 to discuss the possibility of uniting the British colonies in North America. The representatives from Canada did attend the conference, and they played a significant role in the discussions.