I'll second everything decompression said in the first reply.
The island truly has world-class diving. I've dived all over the world, starting in the 1980s, many years in CA (much in Monterey, down to SoCal/Channel Islands), Caribbean, and spent ~1y in Australia - can't think of a single destination that easily beats BC/Van Isl for marine life.
Re: Viz/conditions
As stated Summer can be a bit "murkier", particularly surface/shallows. Most sites a bit of depth will remedy this. Sometimes quite shocking you'll think a dive is a blow-out & you drop another 10-15' and it opens open 10x fold.
So it's a gamble on conditions. Hate to talk up the diving too much & have you wind-up diving pea-soup, as is possible (more so in Summer). We did just get some overcast/cloud+rain for a couple of days so that can be a good thing.
Re: Charters -
From the shop @ Ogden Pt, on many weekends you can do Race Rocks or the Wrecks. Give them a call to see if they're going out.
They're also right there at the breakwater, so you can also do boat dives with them and then a shore dive along Ogden Pt afterwards, if you want to fill your day with easy dives from one spot (also, get fills/warm-up). If you're up for the hike, it's great to dove the breakwater further out (imho). Bit more depth & great life - look in the cracks for wolf-eels & octopus(also found all the way into the shallows/near shore).
Re: 10 Mile
As decompression mentions - top-notch site. Do keep in mind this is a HIGH current dive site. So if you're able dive with someone who knows it/verify your tides to dive it at slack.
Again, as mentioned - if you like walls, Willis Pt is great - easy shore entry, the walls starts really close to shore. You can dive another portion of that same wall at McKenzie Bite - it's bit more of a hike from the parking space. You can easily do both ends of the wall at these two sites.
Re: True competition for best/top diving on planet - North Island
Depending on how long you were staying, or if you could extend your trip to make this a dive trip, the north end of the island offers true world-class/best-of diving.
Search online for Browning Pass Wall / God's Pocket.
After a year in Australia, I'd talked some passionate dive buddies into trying out our chilly waters. These were also divers who've dived all around the world. The dived our north island and afterwards reported back to friends in Oz(& to me) that they agreed it was near top/good-as-gets.
Depending on how long you're here/how much you'll be diving, drop me a message if you're looking for a dive buddy.
I'm boat diving Saanich Inlet tomorrow (Sat) & might be doing charter to Race/Wrecks next weekend, but haven't firmed-up next dives. Might be able to meet up.
Regardless, happy to offer advice/answer questions.
Hope you enjoy your diving on Vancouver Island!
Doug