I am planning on road tripping up to BC from Salt Lake City next summer (2017) for a week. I only have a week to do it so I'm doing 2 days at Whister, 2 days in Squamish, and 2 days on the shore. From your local, infinite wisdom when is the best time to go? early summer when the trails aren't blown out yet? early fall when the temps are good and the dirt has some moisture in it? Being from SLC all I know is dry, dusty dirt that really good in the spring and fall but summers are blown out.
I vote early September: - moisture likely back to tamp down the dust but not rainy season yet and often stlil warm weather - trail crew will have repaired some Crankworx damage in the bike park - alpine clear of snow (bike park and Whistler valley trails), this is not the case in May/June/early July - no crowds
If there's a strong winter, May and early June can be unpredictable for trail conditions, especially higher up.
Pro-tip: one day is plenty for sampling the Shore. Spend the other day in Pemberton, Whistler or Squamish.
You might want to check out the Sunshine Coast. It's a short 40 min ferry ride from near the north shore trails. Awesome trails on the Sunshine Coast and from what I hear (although I'm not inclined that way) a pretty smokin' gravity park. Early Sep sounds like a good plan.