About the children part: Parents can be added to a profile without the parents being married. Just add each parent to the child's profile, as you normally would, and the children will show up on both parents' profiles.
Basically the solution for domestic partners is currently to just not link them, and talk about it in the bio, or do link them, and it will say they're married, but you can explain more in the bio.
I, too, wish that you could have "spouse" or "partner" or something instead of just "husband" and "wife". That way my partner and I could actually be linked for real and not just in the biography section. But I don't want it to say wife on my profile. :P