It shouldn't affect your stay. As Disney resorts go, Contemporary has relatively few rooms, and its proximity to Magic Kingdom combined with the fact that it's the least expensive of the three monorail resorts means it's often sold out regardless of whether there's a convention or not.
I stayed there as part of a convention just last month; this was during spring break, when everyplace is pretty crowded anyway. It was my first stay there, so I have nothing to compare it with, but I'm a WDW veteran and I didn't feel like our resort was overcrowded or too busy or anything like that.