Hezu

That industrial area feel only applies to Hernesaari, which is common docking site for cruise ships (especially the larger ones), but it is not the only location for cruise ships in Helsinki, some ships do use also Eteläsatama (South Harbour), especially Katajanokka side, which is much closer to the city centre, especially the older empire style parts around the Market Square and Senate Square. Also worth a mention that the industrial feel of Hernesaari may some day disappear as there plans to renovate the area, build mainly residential building on the lots that were earlier occupied by cargo harbour related businesses. There has been also plans for a proper cruise terminal. Although these building projects probably won't get into full swing in the next few years as there has been some setbacks on city planning process for the area.

I'm late in commenting, but I have to note that Viking Line ship in your picture might not be true cruise ship since it is one of these cruise ferries that shuttle between Finland and Sweden.

Actually going fully contactless may never happen, already now Finnish legislation (and that might be derived from EU regulations) allows contactless payment only up to 50 euros and then requires that occasionally you have to enter the pin code even if the purchase would fall into category that could be paid also via contactless method. These restictions are of course there to make it less easy for thieves to use stolen cards.

Since I don't eat fish, I won't comment the taste, but when questionable fish products are mentioned, one of the first things that pops into my mind is the Icelandic national dish Hákarl. And then another classic in that category is of course the Swedish delicacy of surströmming, although Sweden was not on original poster's itinerary, but I suppose it would be possible to hop on a train in Copenhagen and make a short visit to Southern Sweden (eg. Malmö).

Actually, some of the LCCs belong to airline groups that also include well-known legacy carriers, eg. IAG may be best known for BA and Iberia, but it also owns Vueling, KLM/AF has Transavia and Lufthansa Group includes Eurowings and Eurowings Discover. This means that on some routes there could be codeshares for these LCC flights and you could combine these with flights from the legacy carriers on single ticket. Of course, mainly these LCCs still offer point-to-point service (and often on routes that can be described as holiday oriented) and the on board experience makes some sacrifies to allow the lower prices.

I think if you choose the smaller roads rather than the motorway route to Porvoo, that might be slightly more interesting, but probably not significantly more interesting and obviously the smaller roads have lower speed limits which mean the travel time is longer. And yes, the historical centre of Porvoo may not be that interesting for the younger visitors. Traditional point of interest in Porvoo for kids is Brunberg factory outlet, which sells variety of sweets. But that is slightly off from the city centre and I doubt cruise lines offer tours that include stop at that candy store. And if you want to spoil kids with products that can harm ones teeth, there is one alternative closer to Helsinki, Fazer Experience in Vantaa offers also brief exhibition tours with a chance to taste some of the products made there.