I REALLY wanna see Sokka (and possibly Zuko's) reaction to this, simply because of the "My first girlfriend turned into the moon" "...That's rough, buddy" exchange. They're most likely not around though, it being seventy years later and all that.
Why should the fact of Yue be a spirit affect anything at all? In my opinion this thing of paring up a human with a spirit is quite normal (and very original too, I really like the idea)! The weirdest yuri couple I ship is a devil with a lolicon zombie (IF she's a zombie, I'm still haven't figured that out...she can be a dead ragdoll or somethin...)
True true haha Nick would never have the balls to do what anyone else did, but the reason is probably for the parents because you know children these days love action cartoons like A.T.L.A and they always have to keep an eye out for any shows that show specific types of content.