"I ask Allah who is the Lofty and the Lord of the Mighty Throne that He cures you"
Prophet Mohammad (Sallallahu Alaihi Wasallam) said that by reciting this dua seven times, the ill person will regain his health and if death occurs then that (death) is a different issue (i.e. death is written it cannot be prevented).
Please let us know his progress he will be in our duas inshallah.
I pray that Allah gives your son shifa and gives him the best of this world and the hereafter. I ask Allah reward you and your family for your patience and that Allah enables you to accept his decree at all times. Ameen