It will cost you a penalty to change your flights to in/out of Vancouver and it will cost you to make lemonade out of your current lemon. Here's another idea that you could consider, but compare the two costs first. And it all depends on how much luggage you will have to cart around and how much running around you are willing to do. If you have 2 cases and a carry on each, the penalty for changing your flights to Vancouver might be worth it. Forego Butchart and substitute with Vancouver's Queen Elizabeth, Van Dusen and Sun Yat-Sen Gardens. Get the most out of Vancouver.
OPTION 1: Fly to Victoria, taxi to a hotel in nearby Sidney BC for the night (approx $20). Taxi to Butchart Gardens (approx $40) for your visit there and taxi back to your hotel ($20). From your hotel, taxi to the Swartz Bay terminal (approx $20) and walk on the ferry to downtown Vancouver (approx 4 hours). On the ferry, go to the Pacific Coach Lines driver's desk within 30 minutes of departure to buy a ticket into Vancouver's Pacific Central Station. (Ask the driver if you can load your luggage on the bus.) At the end of the sailing, make your way down to the car deck to board the coach into Vancouver. Luggage goes in the hold under the bus. From Vancouver's Pacific Central Station, make your way to your hotel by taxi (approx $12-20 depending on hotel.)
** Watch the PCL schedule. The ferries run every hour on the hour in July, but PCL runs every two hours and catches only the odd hour ferries. **
After your cruise, Take PCL from Pacific Central Station as far as Swartz Bay (includes the ferry ride) and make your way by taxi to a Sidney hotel the night before your flight out. Again, 4 hours and the expense of a taxi to the hotel, hotel and a taxi from hotel to Victoria airport.
OPTION 2: Arrive Victoria, take the AKAL airporter to downtown Victoria ($21). Stay the night. Use CVS Shuttle to visit Butchart . Fly Harbour Air from Victoria's Inner Harbour to their Richmond dock near Vancouver Airport which allows 23 kg/50 lbs of luggage. (Flying Victoria to Vancouver Harbour allows 11.5 kg/25 lbs of luggage.) Take a taxi to downtown Vancouver from the Richmond dock ($40). Stay the night. Take a taxi to the cruise pier for your cruise.
After your cruise, taxi to Richmond dock for Harbour Air, fly floatplane to Victoria Harbour, take AKAL shuttle to Victoria airport for your flight out.
**CVS shuttle offers a price that includes admission to Butchart, It is not a guided tour of Butchart, you are on your own and you are free to take a return shuttle of your choice back to downtown Victoria. They also offer a $15? shuttle only fee, you have to ask for it. The shuttle only plus the independent admission fee may total less than what CVS charges.**
If your head isn't spinning by now, you have my admiration. If you don't want to change your flights to Vancouver, I would opt for OPTION 1 as being the least disruptive and the least expensive in terms of additional costs. Ultimately, my recommendation would be to change your flights to Vancouver and pay the penalty. I think you would have greater peace of mind, less running around, more time to enjoy Vancouver - including our 3 nice gardens.
CVS Shuttle: www.cvscruisevictoria.com/butcharts.html
Pacific Coach and BC Ferries: www.pacificcoach.com which rides on www.bcferries.com
AKAL Airport Shuttle: http://www.victoriaairportshuttle.com/
Sidney BC hotels: tripadvisor.com/Hotels-g181772-Sidney_Greate…