Actually, I would just suggest dressing up as Vikings. Heck, a character from a children's movie? Do How to Train Your Dragon.
It is 100% proof. You can dress as any of these characters, we Scandinavians won't give a single flying fuck if you do. Dressed in a large body suit that is whiteskinned to represent one of the larger characters? We don't care. You're any non-white skin colour and dressed as a Viking? We don't care. You whiteface to dress as a Viking? We don't care. Doing a Scottish accent for some weird reason even though it sounds nothing like us Scandinavians? We don't care! Scottish sounds awesome anyway!
If someone complains, we Scandinavians will personally go to their house and beat them cause Vikings rule and everyone should be able to dress up as them! It is the 100% proof Halloween costume that people overlook cause I guarantee you, we don't give a shit here in the North. You get to be a fun character from a different culture that takes no offense to anything you can do. Why? Cause we're bloody Vikings that's why!