For your first day, I would recommend "the grand tour". I believe this is detailed on the trail map, but basically it is quite possible to hit most major areas of both hills in a day to get an overview. Many people find it helpful to go with the free guided tours leaving several times a day from the top of the Solar Coaster on Blackcomb and the Roundhouse on Whistler.
I treat Whistler skiing quite differently than smaller hills where you just go round & round on the same lifts & runs all day and compete for pow. If the weather or snow isn't to your liking in one area, go somewhere else and it will be completely different. Rather than concentrating hard on technique, tour around on your skis. Check out the scenery in various locales. Have a beer and a snack somewhere like the Chic Pea, feed the Whiskyjacks and watch the world go by. If it snows the night before, no need to be first in the lift line... plenty of pow for everyone, and it doesn't track out for days if you ski the trees or walk 100m or so. The long runs and high-speed lifts will give you all the vert your legs can handle, so don't overdo it by trying to master the place in 3 days... can't be done. Going to Whistler is more a total vacation experience, though the skiing is pretty good too. Relax. Life is good. There may not be great skiing in the lower 2000' at that time of year, but the good stuff is above that anyhow. The World Ski & Snowboard Fest www.wssf.com
is on in April, and always fun. You can't help but enjoy yourself. Take the shuttle from the airport rather than renting a car. Enjoy!