Vancouver is world class but small, no more that 2 -3 days. The city is a base not a destination.

Whistler-Sea to Sky corridor 2-3 days. Base yourself in Squamish or Pemberton and skip staying in Whistler. Both are only 30min drive from Whistler.

Gulf Islands 1-2 days or longer if in the summer. Vancouver Island is too big to explore meaningfully on such a short trip.