Being that the Caribbean is the most common and largest number of cruises, it certainly is in error the above post that Alaska has "a much younger crowd". It clearly does not, with the bulk of passengers middle aged and above on all lines.
Egad! Have you ever taken a cruise to Alaska?
I have taken two cruises to Alaska, and have encountered a younger crowd on both of those cruises than on cruises on the same lines to both the Caribbean and the Mexican Riviera.
It may surprise you, but Alaska attracts a very high percentage of first-timers and very few passengers who return there time after time. On my first Alaska cruise (aboard MV Sun Princess in August of 2002), I had the most days at sea with Princess on the ship -- the only time that I have been in the "top three" who receive awards (or at least who then received awards) on a Princess cruise.
My opinion only, budget fully for costly excursions, you get only half a trip without them. I would never recommend foregoing them.
That depends what you want to experience in your ports of call. In many cases, the moderately priced excursions such as a walking tour or the visit to Saxman Village in Ketchikan actually encounter more of the indigenous culture and the history of the region than, for example, a "flightseeing" or four-wheel-drive trip. I strongly recommend the ride to Summit Lake and back on the White Pass & Yukon Route in Skagway, though!
From Whittier, the Seward Highway is the EXACT same routing as the RR, so it is not recommended unless you take the regular run, the cruiseline contracted is too costly.
IIRC, there are a few spots where they diverge between the Whittier Cutoff (which the guides do point out during the ride) and Anchorage. In one such spot, the railroad literally runs along the side of a cliff broken by short tunnels and the view of the canyon is really awesome.
And in any case, the railroad offers (1) larger, more comfortable, seating, (2) the option to get up, wander around, and stretch your legs, and (3) food and beverage service that are not available on the bus. That alone is well worth the difference in price.
The above resturant reference in Talkeetna is the Latitude.
It's called "Latitude 62" rather than "62nd Parallel?" Okay, thanks for the correction.