Victoria is a port of call on most Seattle and Vancouver round-trip Alaska itineraries, and the ships dock rather than tender, at Ogden Point on the south edge of the city. Many Seattle-based ships call in the late afternoon or evening for a few hours; Vancouver-based ships and repositioning cruises more often arrive in the morning. Check your own itinerary for the hours before reading any further, because they decide everything.
Getting from the ship to town
Ogden Point is about two kilometres from the Inner Harbour, a 25 to 30 minute walk along Dallas Road and through James Bay, flat and pleasant in daylight. Shuttle buses, taxis and horse-drawn carriages wait at the terminal. Tours that pick up at the pier will say Ogden Point or the cruise terminal in the meeting-point note on their Viator page; tours that meet downtown expect you to get yourself there.
What fits the time you have
The Butchart Gardens from the ship
The Gardens are 35 to 40 minutes north of Ogden Point by road, so a visit needs about three hours in total and is usually done as a pier-pickup tour that includes the entrance. The Gardens stay open into the evening in summer, with illuminations after dusk, which is what makes them possible on an evening call. The public bus from downtown takes about an hour each way and is fine for a long daytime call but too slow for a short one.
Whale watching on a port day
Victoria's whale-watching boats leave from the Inner Harbour and Fisherman's Wharf, both a walk or short taxi from the pier, and most trips are three to three and a half hours. Operators are used to cruise passengers and will tell you which departure returns in time; choose one that leaves at least two hours of margin before all-aboard, because trips can run long when whales are far out. Evening departures exist in summer, and sunset trips can suit an evening call.