If you're looking to join a club to get help with training & racing, then you're probably better off joining a tri club rather than separate sport clubs. The Pacific Spirit Triathlon Club is very popular http://www.pacificspirittriclub.org/
In terms of sprint vs oly, depends on when & where you want to race. And then how much training can you get in before that day, and if you want to run 5 vs 10k? Pick a goal, set a plan & stick with it.
It's great that you've already had some experience in tri as part of a relay team. And if you can bike the 90k, I imagine there's no reason you wouldn't have enough endurance to do an Oly. For me, I did my first tri last year at UBC. For me, I chose the sprint distance because the swim was the thing I was most worried about.
Tri clubs in Vancouver: there are a lot of them. I'm a member of the North Shore Tri Club, which is more of a social club than a coaching club. We do rides Wednesday and Saturday starting in the spring, and more importantly, pub nights every month