Pushy stepmom vs. controlling exwife with son/dad in the crossfire?

My new wife who is a wonderful stepmom I feel sometimes does things just to "push" my exwifes ons(example-attends p/t conferences). But my exwife also does things that "encourges" my new wife to act this way(example-fliped out big time when new wife attended p/t conference). My exwife goes out of her way to make sure my new wife has very little involvement with my son outside of my house. And my new wife goes out of her way to try and "push" herself in. I fear all these "issues" and thier haterage will affect my young son. How should I handle this?