If you have any interest in a small ship cruise, check out Lindblad, http://www.expeditions.com; an entirely different milieu. Any where we decide to go, we check first to see if they have a trip.

If it's in your budget, I would strongly urge you to consider Silversea. It's a small (just under 400 passengers), all-inclusive, luxury line and the experience is absolutely unbeatable. We did Alaska with them in 2006. Rooms are spacious, as are the verandahs with enough room for two teak loungers and a small table; bathrooms are ultra-luxe with a long, deep tub and separate shower; food is excellent and service is warm and top-notch.

(Don't know the age of your parents, but from my knowledge, the Lindblad line includes things like climbing into Zodiacs for up-close nature viewing.)