I also used to dislike the bureaucracy of marriage like some people here, but I noticed that I do enjoy the "connection" aspect of it. (it also has some legal benefits, so I may end up following through in a few years)
As for children, I don't think that would ever be a good thing for me, I really have no trust in myself for raising them. I strongly suspect they would always feel alien to me.
Fimm
The first half of your post is basically my thoughts but written better. I also relate to what you say about being more able to imagine yourself as a single parent than in a childless relationship, although I still ended up trying to have a few.