All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
First of all, we ask Allaah to make better your solace for the death of your son, and we ask Him to grant you his intercession on the Day of Judgment and bless you with someone better than him.
However, we cannot definitely say what kind of reward that he will get, as this is part of the unseen which only Allaah knows, but it is confirmed that whoever dies as a Muslim, he will be admitted to Paradise. Abu Hurayrah narrated that the Prophet said: ''It is only a Muslim (believing) soul who will enter Paradise.” [Al-Bukhari and Muslim]
On the other hand, calamities wipe out one’s sins; Abu Hurayrah narrated that the Prophet said: ''A believing man or a believing woman continues to be afflicted in his/her own body, wealth and children until he/she meets Allaah free from sin." [Ahmad and At-Tirmithi]
Allaah may also bless your son and grant him the reward of the martyrs in the Hereafter because of suffering from this magic. It is reported that the Prophet said: ''…and he died in his bed by any kind of death (i.e. whatever reason was his death) Allaah had willed, then he is a martyr and he will be admitted to Paradise.” [Abu Daawood - Al-Albaani classified its chain of narrators as Hasan (good)]
Moreover, Al-Haafith Ibn Hajar reported from Ibn At-Teen in Fat'h Al-Baari that he said commenting on those who were reported to be among the martyrs of the Hereafter: “All these are difficult kinds of death in which there is a great Favor of Allaah on the nation of Muhammad as He made them a means of wiping out their sins and increasing their rewards, by which Allaah made them reach the status of the martyrs.”
Allaah Knows best.