I don't believe the body forgets, but as the mind heals and accepts, I believe the whole self can heal.
Especially in the young, the trauma seems to transfer into a unique way of seeing the world.
As we look through many of the greats of history, or the greatest people I've known....they had awful trauma, many of them. But they used the feelings and skills to transform their corner of the world where they could. Even if just in having deeper relationships, trauma can ultimately be transformed.
I do believe I had PTSD from an early age. I didn't get disgnosed until a year and a half ago. But I can see some gifts this terrible disease has given me. One of them is an immunity to 'going along with the crowd' and that has been very freeing when the crowd is dead wrong.
Your son will have memories of you loving him and helping him. He will be able to comfort himself with and teach that 'love in action' to others.