Ports and itineraries.
You are pretty much guaranteed to do the 3 port Inner Passage + a glacier viewing day. The variations come by adding Sitka or Icy Strait Point, perhaps Haines (rare). Glacier Bay is beautiful, but is restricted by permits that are mainly held by Princess, Holland America Line, Cunard, or NCL.
I have sailed Princess and NCL on Glacier Bay itineraries. While it is a nice day of viewing multiple glaciers, it could get old for some. I actually prefer visiting College Fjord, done on a Northbound (one-way) cruise from Vancouver to Anchorage on Princess. You can see many glaciers at a time from several locations in a shorter period of time (and end up going to Anchorage - we then took the train, 12 hours, through the interior to Fairbanks before flying home.
It is easy to spend a lot of money on excursions - and do a lot of once in a lifetime adventures - thanks to the beauty of SE Alaska. Helicopter or float plane flights cover a lot of territory, especially over the Tongass Forrest near Ketchikan or the glaciers out of Skagway (done both). Whale watch tours from Juneau. Summer training camps with dog sled teams. A train ride up the mountain from Skagway.
You can hike, bike, raft. Visit wildlife centers, gardens, or culturally-focused education. The excursions are fairly standardized from year to year and on all cruise lines. I would imagine there may be some Disney ones with their own touch, but the beauty of Alaska does need enhancement.
I am a fan of whale-watching excursions and a visit to Mendenhall Glacier (often doing a combo tour of these while in Juneau). Whale watching is somewhat like watching soccer: you spend a lot of time waiting for something to happen. If you turn away at the wrong time, you might miss something spectacular. But it is fascinating to see flip of the tail or a breach out of water. And it’s a boat ride in a spectacular setting.
(My favorite whale-watch combo was in Icy Strait Point, combined with a zipline ride, seated, of nearly a mile long. Wow. Could do that every year.)
Over the years, our family has done
Whale watching
Mendenhall Glacier
Helicopter tour with glacier landing
Float Plane over Tongass Forrest with lake landing
Zodiac boat excursion, Ketchikan
Visit to Haines with boat excursion
White Pass &Yukon Railway
Lumberjack show, Ketchikan
Bike, Hike, and raft
Kayaking
Ziplines
Rented car for drive from Skagway to Whitehorse Yukon Territories
Walk Around Ketchikan and Skagway (no need for transportation to get the feel)
Enjoy crab at Tracy’s Crab Shack or fish and chips (both Juneau)
Some activities we repeat, others are a one-and-done.
Some have been booked through a cruise line, some through independent operators, and others DIY.
We have sailed mid-May, late May, late June, mid-July, and early September.
The weather has not been significantly different from cruise to cruise, but it can vary from week to week. You just pack and dress in layers. (Sure, our mid-July was warmer, but I still needed a coat). Unlike a Caribbean cruise, a 10 degree variation in temp is not as significant.
Early- or late-season cruising can mean an activity is not running (lots of college students work here). Hotel costs pre-cruise or flights may also be less expensive. Vancouver is not a cheap pre-cruise hotel stay, nor are flights to Canada.
…There are lots of threads on this forum regarding various aspects of cruising to Alaska. But ask away for direct questions. It’s easy to talk about this destination once you have experienced it. It brings up good memories.