Glad to see that things are coming together for you. Your plans sound great.
I can't believe the pre-trip that Olivia is suggesting and it will involve at lot of flying.........but folks say that Denali is worth it.
You can bet that there are organized day trips to Butcharts that will be bus and ferry and will probably be the easiest way to go. The bus gets preference on the ferry and will drop you right off at Butcharts. You won't get to see anything of Victoria, as the garden is about 20 Km north of the city and fairly close to the ferry terminal.
If you did take that float plane over you may want to spend the night and then hook up with a Butcharts tour that will take you back to Vancouver on the ferry.
The Garden is truly spectacular and worth the trip. In September it will be dahlias and roses and hydrangesas other Fall flowers. They change the appearance based on what is in season.
Now you are going to have to live up to the Aussies that were on the Western Caribbean cruise. They were truly a fun bunch and livened up the whole cruise.
H & G