Although I'm a Finn I can see where the negative comments of the American parents come from. You have grown up with the Disney policy of showing children only sugarcoated films trying to protect them from the real world. I am a great fan of enchantment, princesses and cute animals but to make changed versions of world classics such as The Little Mermaid in which the ending was ruined by changing it into a happy one is a sacrilege. The Andersen story is forever spoiled for those who have first seen the film.
I don't actually believe that children pay much attention to the one night stand or the macho behaviour of the reindeer. That's there for the grown-ups. The children are drawn to the story and if you don't point the other matter to them, it goes by like a snowflake.
On the other hand many children living with a single parent may relate to Niko's situation and find comfort in seeing that he is not an outcast. It would be wonderful if all families had two parents and everyone lived happily ever after but sadly it isn't so. The word bastard should be deleted from the world. Your own goals and resources are what matters, not your family background.
As mentioned in another post the animation of snow is fantastic in this movie. Also the animals are drawn well. The reindeer really look like this and the wolves' running rhythm is spot on. There are many local details like the landing light on the runway. They are called lumberman's candles in Lapland.