I agree with you about Mikkel, Onni, Sigrun and Tuuri, probably also about Reynir. But I am less sure about Lalli and Emil. Emil strikes me as more the Gryffindor type, or maybe, like Harry in the original story, someone who might fit in either, but urgently doesn’t want to be in Slytherin - remember the bit with the Sorting Hat where it is speculating where Harry fits, and he is going “Not Slytherin, not Slytherin!”? Whereas Lalli, although he has some of Onni’s ‘must keep everybody safe’ thing, is also okay with killing if he must, and is a sniper and a night scout who is good at stealth, which strike me more as Slytherin traits. Yet he is also courageous, willing to put himself in danger or even to spend his life and burn out his magic for the sake of others. And to be a mage, especially in the Finnish style, he would need the sort of intellect, creativity and memory which one would more associate with Ravenclaw.
Complex types, both lads.