Even if it is post partum, (which it could be) the psychosis can be just as severe and scary. But she still needs to see a doctor regularly for treatment. You need to sit your son down privately and have a heart to heart. Leave the children out of it for now, and just talk about getting her well. Express your concern for her well being, tell him what you have observed, tell him that you want her to go back to the doctor because she needs regular monthly checkups with post partum disorder, and trust the doctors to do the rest. The seroquel will calm the mania and the psychosis but it won't regulate her moods, and it sounds like it's no longer working very well on the psychosis either, so she needs a check up to get her meds worked on again.
I don't mean to suggest that your concerns about the children aren't very important. They certainly are. If she gets truly psychotic and your son remains steadfastly in denial, you may need to do the truly frightening thing and call in child protection services. You can't take the children from the house yourself, but you can call and register your fears and let the professionals check it out. I know that would be heartbreaking, but as a last-place measure, it is an option you have to protect those children.
Co-Moderator, Bipolar Forum