rozied,
Sending you hugs from another mom. Your ex had no right calling your parents and pulling them into this again. You are right a lawyer may not be able to help your son and if that is the case your parents money can't help. Don't do anything that you will regret later, cut your parents off at their age. Take time for you and turn this over to your HP.
For a lot of reasons I did not speak to my family for 15 years, and found out my mom was sick. I did try to talk to them and see them, but the rest of my family did not want me near them. When mom died in Feb, I was at peace because I tried. My mom died at the age of 69, you have had your parents longer so please don't cut them off agree to disagree on this matter.
Hugs and prayers coming to you