Jesus, I can only imagine what will happen when you guys have a second kid, wife says first kid gets to go in the kitchen or outside, the cat gets pushed further, outside or leave.
When the second kid comes along, the first kid will play up because he'll go from 100% of the attention to 10% of the attention. He'll be frustrated, not understand why his life and home have changed, why his mum is spending most time with his sibling and act out.
Cat's are in effect no different. You turned it's life upside down and it has no clue why and it's gone from being treated like a family member to being treated like a nuisance. Actually spend time with the cat, spend time around mum and baby and get used to being at home. Cat's peeing in the house do so because they are stressed, new house, new kid and being ignored are all stressful. Make the cat feel at home, let the cat feel part of the family and it will stop being a problem.