The polyamorous folks who have children that I know don't seem to have this problem--their observations and questions are, by and large, the same ones that anyone else with kids has.
Whoa.
Now--who does have it different? I'll tell you who. Single parents. Man. To the parents on my friends list who are "flying solo," my profound admiration and respect. If you ever need a night off or a hand with something just let me know.