Well, Niagara Falls is about a 4 day drive, or 5 hour flight.
I'd try the Aquarium, shopping on Robson Street (spelling??), hit up Stanley Park. You can also climb Grouse Mountain (the Grouse Grind) and take the gondola back down if you want something athletic. Granville Island has lots of shops and restaurants. I think there's a brewery there, but it's been a while since I've been. There are tons of great restaurants, though I have no suggestions at the moment. But you can check online for reviews. Check out Gastown too for food and shopping. Stay out of East Hastings. It's a pretty dodgy area. That should get you started. You can check TripAdvisor too on their forums for suggestions
ETA - Dr. Sun Yat Sun Gardens, Kitsilano beach, head up to Whistler, Cypress Mountain (sp again) if you want to ski. They might have summer stuff there too.
Re: Vancouver canada honeymoon