I think I would go with the black watch semi-trad. It's still a dark tartan, but it also looks more like a traditional than the swk's.

Also, if you're going with black sporran and black argyll, do a black tie as opposed to navy. A friend of mine mentioned at a recent funeral that navy is the one color you don't want to wear at a funeral, as everyone else will be wearing black. And a black tie will go better with the black accessories anyway.