Funny you should mention that...
I'm planning to be on Vancouver Island around that time also.
Last year I went on a whale watching outfit out of Tofino and had a nice time. I think that all of the outfits out of Tofino offer a fairly similar experience and the guides find where the whales are by looking for other tour RIBS. Pretty much all of the tour RIBS out there are made by either Polaris, Titan, or Zodiac Hurricane. If you go on a tour from Tofino, you will see grey and perhaps humpback whales and maybe Orcas. If you go on a tour operating out of Victoria you're almost certain to see Orcas (I kinda wish I took a tour from Victoria rather than Tofino last year).