All the ships I have been on are absolutely beautiful: Seaside, Seascape, Seashore, Meraviglia and not too far behind Divina. I am sure my upcoming World Europa and Euriba will not disappoint either!
I was on the 5/14/23 Transatlantic from NYC and we did not stop at Isafjordur. We were told it was "port congestion" which was a flat out lie. I do not believe any of the Prima sailings have made it there due to the real reason of the dredging/port construction not being completed.
We do both next 5 are with the Yacht Club as Haven has priced us out. Haven would be at least 2x as much as what we paid for Yacht Club at the time. However, Yacht Club pricing has also increased dramatically lately, still much more affordable than the Haven.
I would wait until you complete your Seaside cruise to make a decision. The Seaview and Seaside are pretty much the same ship, then you will know if you would like to sail that class again or even if you would like to sail MSC again. Maybe you will want a different class and try the World Europa instead. Or maybe MSC will not be a good fit and you will stick with Celebrity...If you have never been on a European Mediterranean cruise, I would say all the itineraries look great!
Your son can do the same things on the Joy that he can do on the Icon. I would book the Forward-facing penthouse on the Joy in the haven for the same cost as the Icon.