T.M.
Well, you need to lay in bed tonight and pray about it, you will hear a little voice that will tell you what the right thing to do is.
Also, your son is 12, let him know all the options and let him help make the decision as well.
My mom had to decide whether or not to have my 9 yr old sisters head sawed open to remove a brain tumor with the 50/50 chance that she would die on the table. Sometimes we get faced with these and there is no easy answer. I think I would do all the most non evasive things first, make sure I've gotten plenty of dr's opinions, and then ultimately make the final decision.
Prayers to you for courage and discernment.