We went on the Alaskan cruise after two weeks in Canada including the Canadian sleeper from Toronto to Vancouver and the Rocky Mountaineer. It was probably our best holiday ever, and I’d do it all again in a heartbeat, so I’m very jealous!
We had at least two formal nights on the cruise, so took outfits for those, plus warm jackets, walking boots, thick gloves and hat for going on the Athabasca glacier, and plenty of Summer clothes (it was August). I don’t know how we fitted it all into one suitcase apiece, but we did! We went with Air Canada, and I think the luggage allowances were quite generous.
We did make good use of a laundrette next door to our hotel in Vancouver before boarding, but there’ll be facilities on the ship too.
Have a great time - I’m very jealous!