Many better than me to expound on this, but I skied there in late April 2002 I believe and I couldn't find one rock or bear spot on Goat's Eye. I think it had been an outstanding year, conditions were great that late. I think they also have race training in May many years at Sunshine.
It will be crowded on Easter Weekend, but most of the public non-Catholic school boards in Alberta have their spring break in late March, so the week days will be good. Snow is usually quite good at that point and doesn't really get soft until late April.
Lake Louise and Sunshine are in general good late season areas in terms of snow preservation. 2002 was a good year for the region. If it's a lean year the rocks will start to come out by mid-April in sun exposed areas, Goat's Eye at Sunshine, off-trail on the front side of Louise.
Since you're going in April, you can wait until January to book and see if it's a decent year.