Just did this last year on the Spirit. The only thing I would add is that if you're on the Spirit, it's the only ship with Soul Play, which is a free of charge painting class/activity. My wife really enjoyed that. Agree with all the rest. There is a naturalist, they have a few other activities (I specifically remember axe throwing - foam/velcro axes, not real ones - on the Lido deck). There was a local Alaskan singer/story teller.