As a realtor and not a legal expert, I would encourage you to consult with an attorney. However, if its just removing your son off the title you can have him transfer his ownership to you by quit claiming the property. He would sign a quit claim deed and you could record it at the county office of the recorder.
I think if you called the county recorder's office they could tell you exactly the best way to handle this. I'm not sure quit claiming is what they would recommend, since there is family involved there may just be an easy what to transfer ownership entirely to you. The county recorder can let you know of the proceedure and costs involved in getting this done.