Yes, La Veranda is definitely the place for as quick breakfast prior to excursions, if not the other choices mentioned above. Compass Rose is not speedy. In Concierge suites, you wait and tell your steward what your preferences are. I would call and ask if there's a waitlist for the cooking class.
I can't comment on specifics, but if by "land", you mean at the airport, then the question becomes, where are you staying? After a long flight, your hotel restaurant might be just the thing. Bear in mind that most hotels aren't close to the port or food trucks, but some hotels have restaurants nearby.
I wouldn't call it a plethora. Depends on the state of renovations at these places, and changes of ownership. We stayed twice at Le Meridien and it's now named something else and is temporarily closed, presumably for renos. Hotels don't last long in this climate. The Hilton has been renamed and renovated a few times since I was first there in 2000.
How about boat trips? We did Lamanai twice from Belize City. Yes there is a bus ride, but not too long as I remember. Then a fairly leisurely boat ride up a narrow river full of wildlife to the magnificent Mayan ruins. Boat trip and bus ride back. We loved it enough to take a friend back there.
Again at Santo Tomas we took the paid trip up by speedboat and then by a slower boat up to see the Maya refugees who live in the Qe'qchi village. It also, back then, included lunch in the town of Livingston, a Garafuna town which was also very interesting. The speed boat ride was a bit harrowing, take a hat with a strap or otherwise cover your hair!
If I remember correctly there is an option to not go into the Yukon, or at least not get off the train, thus avoiding Canadian Immigration. We did this one years ago, perhaps it's still offered?
The standard balcony suite are lovely. Avoid extreme aft suites if you can due to vibration. Great theatre, great aft lounge, with balcony. Small, intimate ship, cozy at times if weather is bad. A bit bouncy in heavy seas.
I'm not a single but we've befriended singles in the past. No need to just stick with other solo travelers. Trivia, excursions and shared tables are good for facilitating mingling. Many couples are not joined at the hip.
That's disappointing, don't remember this in the past. As for CR, there's no excuse for bad acoustic architecture--this should be integral to the design from the get-go.