Welp, polygamy nearly always has jealousy involved - polygamists admit this themselves. There is one true story where a guy was so jealous of others in the polygamous relationship he killed the resulting baby. Beware of the green-eyed monster. Many polygamists have babies. Like shadow said, if you can take proper care of children (not just financially - be there for them and protect them mentally and physically, this world is full of pedos and baby snatchers!), even if you as a couple split from whatever, then do it!
The child might be bullied at school and confused about your family structure and what not but that is something you have to deal with no matter what.
In case you don't already know, this is AUD avg cost of raising children (I know its old info but it doesn't change much rn):
You must understand that the jews are going to try and make it nearly impossible to live in the next few years. Of course we are trying to stop that but you must consider it as a possibility. Do you really want to bring up a child in conditions like this when it's already hard? People here might be well off (now) and encourage having children without a care but there are many people knee deep in debt to the government (and regret) because they had children. It is good to consider both sides of the coin and have a good think first.