I would certainly ask to do this. Do find a lawyer who will be there for you, you will need that, and don't back down on the abuse issue...
My heart goes out to you and your son. Let him know you love him and will be there,
Have you considered having your son seen by a child psych? He may be able to express how he is feeling with this storm raging around him...and about the things that have been done to him.