@Hannah thankyou x
Not been on a cruise but with pyjamas think how warm or cold you'll have the heating/air con. We went to Egypt and while it was mid-late 20s, I packed warm sleepsuits as I know my partner likes the air-con cold. Also bare in mind babies can't go in the pools on cruise ships, some have splash pad type things they can so check if there's one of those before packing swim stuff for baby.
Make sure you take more than enough nappies, the Nordic countries are SO expensive. We love our Snoozeshade for the evenings out while she sleeps in the pushchair x