My situation is slightly different, as I left Norway for London at 21, when my parents were still quite young, my mum 58 and my father 66. I am 37 now, and have lived in Norway again for just over a year.
I met and married my husband, we have 2 children who had grown up in London. Our oldest had started school, and they were "londoners", never considered my Norwegian heritage other than when visiting their grandparents twice per year.
After 16 years in London, a lovely little house, good jobs, settled and happy, when our oldest was 6 and our youngest 3, we were facing some pretty tough choices and I found I could not live with myself with such a distance to my parents.
My mum has incurable cancer, and started suffering from memory loss. She started being really confused, mixing up cooking times, dates, could not remember my birthday, and other vital facts you take for granted that your parents know. She is my fathers carer, as he is paralyzed after a stroke just before our oldest was born. I could no longer close my eyes to the fact that there were 2 elderly people there, who were facing old age and ill health all on their own with no child to even look in on them.
I figured, they had given me all their love and care when they brought me up, and love is a two way thing, you cannot receive throughout your life, and turn a blind eye when the roles reverse and the parent need a little parenting him/herself. It is a decent thing.
Your father is young now, and as long as he is happy and healthy, you have really no particular obligation, I suppose, unless you count in a relationship between your kids and him, as an obligation to them both/all.
But you need to know that a few years down the line, you have to take responsibility for the choices you make today. This means either closing your heart and turn a blind eye, or uprooting a settled family from a life they love. In either case, if your life pans out like mine, you will be between a rock and a hard place, and I dont envy you this.
So, is there nowhere else in Europe where you can have a life you describe?
From your description, Norway seems to fit the bill. Find work outside Oslo, and you are a short flight from the UK, with low crime rates, good schools, nature, fjords and mountains, and the weather is usually sunny and warm, but not warmer than in the uk. (I am across the polar circle, so we are covered in snow from November to May)