Hold the phone! I've cruised about a dozen times, on four or five different lines. Here are my thoughts:
Food safety: IMHO, no different worries than in any land-bound restaurant. I have never been sick from food, nor has my husband.
Illness on cruise ships: any time you have a thousand people together, somebody will get sick and share the "wealth". We always use Purell etc., wash our hands frequently, don't touch elevator buttons, door handles, etc. with hands (we poke buttons with our elbows). You'd have the same problems in a school or large workplace where there are lots of people around. Norovirus ins't exactly an exotic, rare infection. Just ask a daycare worker. If you have a compromised immune system (as I did at one point), take extra precautions or choose a different vacation. By the way, I've had serious health problems since 2006, and cruised several times in those circumstances. I spent a lot of time in Celebrity Solstice's infirmary, some in Coral Princess's and also in Oceania Regatta's. All had very professional health care providers who were good at what they do: deal with people who have acute and chronic problems during their vacations. I wouldn't hesitate to visit the medics on any ship. Solstice's team had to provide me with infusions of antibiotics over several days, and I couldn't have been better-cared for by my own doctor (who just about walks on water). I also had a good experience with several acupuncture treatments for lower back pain while on Solstice.
Cruise lines: Yes, Holland-America is skewed "older", more genteel feel as I hear from those who sail with them. We had bad experiences on a 4-day cruise on a large Royal Caribbean ship 11 years ago, and on an older NCL (Spirit) three years ago. The food was, frankly, poor and the service perfunctory. Here are my recommendations for Alaska: Princess- choose a smaller ship like Coral Princess or her twin, Island Princess. I think they have about 1975 passengers on board. Fewer people than the huger ships (less chance of illness, possibly) but also, its smaller size allows it to get all the way into College Fjord and Glacier Bay, which are the prime jewels of any cruise to Alaska. We cruised on Coral in Alaska and a few years later on a Panama Canal cruise. Oceania has even smaller ships (685-1250 passengers) and are pricier, but they have excellent food, superb service and excursions for experienced and novice travelers wherever they stop. Definitely upscale and pricier, but they are running 2-for-1 cabin pricing, airfare included, gratuities included, and some cash for onboard expenses. We cruised in the western Med with them. Celebrity is the upgrade brand of Royal Caribbean. We've been on Solstice (2850 passengers) in the eastern Med and were on Summit last week, its first week after a total re-do in drydock. Summit is about the same size as Coral Princess, and we liked it a lot being part of the first group to cruise on her since overhaul. The food is good and excursions aren't too pricey. Excursions in Alaska will run higher than in the Caribbean, so when you look at that, please compare region to region to get a better idea. Princess was first, I think, to "do" Alaska, and their excursions were great in our opinions. Be aware we did that cruise in 2004, though, and Panama Canal in 2007.
Whichever line and ship you choose, it's worth checking out what they have for people celebrating special occasions.
I have used CruiseCritic.com for information, but please keep in mind: opinions there are just that, opinions. They've drawn heat in the past when it was learned some of the "members" were shills for the cruise lines, so caveat emptor. On the other hand, I got a lot of helpful information there, too, including using Captain Larry's Orca Adventures for whale-watching out of Juneau. You can find my reviews there under the same screen name I use here.
Enjoy your cruise!
***It is better to ask forgiveness than beg permission.***