Good for you DS...although this isn't really a darkside for you if you were open about it from the getgo!
Anyway, from what I gather this post is just about you finding a place to find some counsel while you are waiting for your wife to have the capacity to revisit poly. You have stated you were clear that you wanted a poly family situation.
1. Why did you not establish other relationships before the children?
2. Interest or curiosity are completely different than embracing a lifestyle, are you sure you weren't confusing the two when you discussed the idea of a poly family in the beginning of your relationship?
3. Did you talk about it more than once? ( I know this sounds sarcastic but it is not, sometimes the fellas think one discussion= decision...NOT!)
4. Are you hoping to start a relationship with someone soon and don't know how to tell your wife of this interest because of her pregnancy and other stressors?
This is a good forum (SUPER-opinionated people) with lots of different perspectives and approaches. I am sure you will find the resources you need. I wish you the best in your search and hope you can both enjoy your lives...unhappy anyone is not a good thing. Hope is alive here.