I think it's wonderful that the biological mother to your son is making a consideration for both children in that your son will have a bio sib, as well as an emom considering they'll be together too. I've known of cases where an emom didn't thinkh this, and so released the other child to another family in order to 'make someone else happy'. I'll never understand that one.......
Anyway......I think to put this in perspective, you'd have to think this too: "What if you'd become unexpectedly pregnant and already had your son as you do now?" Wouldn't you just find whatever means to 'make it happen' and go from there?
There's always WIC and other programs if you need this, in order to get through it all. Heaven knows, you'll not be the first person/couple to need help with anything during these times of economic turmoil for so many.
Go with it. Deal with it. As others have told you here, you'll be so glad you did...and everyone will benefit in the long run.
My best to you!
Most Sincerely,
Linny