I’m originally Scandinavian, lived in Denmark and Sweden, have lived in the UK for 15 years now, apart from 1+2 years five and nine years ago.
Language wise, you will be fine. Like others have said, everyone speaks English, and you may find it hard to get practice in the language of the country. There are masses of expats in all big(ish) cities, so you can get ample doses of ‘home’ too, if you want to. It is easy to get stuck in those circles though, so I would make an effort to try to meet some locals too. Meeting them through children is a great option, would be easier if you put them in local schools. You will need to make an effort to learn the language, especially, perhaps, if you don’t know any other languages already (always a bit easier when you’ve understood the ‘concept’ of other languages, and how they can be constructed completely differently to English) but it can be done.
The one thing that I now dislike actively with Scandinavia is the attitude that there is ‘one solution for all families’. There is a certain snobbism around the view that ‘we’ve sorted out the answer to women working + childcare + work/life balance, so the world should follow our example now’. So if you want to go for a different solution (for example, if you don’t want your children to be in full-time daycare from the age of 1 (or less – 6-8 months in Denmark), you are certainly the odd one out, and you’ll be considered odd. I had a discussion with an Australian man who’d moved to Sweden to be with his (German actually) girlfriend, and he was saying that he wouldn’t mind being a full-time dad, his girlfriend had a good job, ‘at least for the first 4ish years’. I had to tell him that he would be a very lonely soul: nobody stays at home for that long in Scandinavia, everybody works, and most work full-time, or close to full-time, so he would have nobody to meet up with, and his child would be a lonely soul. And the whole society/funding/taxes system is based on the premise that everyone will work. Unless your spouse earns masses (and that’s hard when taxes are that high), or you choose a very frugal life-style, you will struggle to live on one salary. Childcare, however, is extremely cheap, compared to the UK – obviously since everyone is encouraged to work asap again.
That said, if you can live with this, and like this one solution ;-), you will likely have a much better work-life balance than in London. Especially spring and summer/early autumn are great, people work much less in general, but even more so in the summer; lots of time spent outdoors, and family activities are actively encouraged. Men take paternity leave – in my Scandinavian circle of friends of highly educated men, including judges, doctors etc, all have taken at least 6-8 months of paternity leave. Dads are expected to, and do take a much more active role in rearing children (that is one thing I cringe a bit about in the UK: the attitude I see/sense from some mums that men just cannot be as good as women at caring for children). It would be unheard of for families to have a set up like the one I see of a lot in London; that dads work such long hours that they don’t see (or hardly see) their children during weekdays.
I’d suggest you join an expat group in Copenhagen and/or Oslo just to get a feel for what people who are there right now think, and how they’ve found their feet. Or, if you feel up for it, go for it – if you go soon-ish you’d likely get permanent rights to stay, and it could be an adventure for a while even if you don’t end up staying your whole life.
Good luck!