Dear Aineo
I am aware that the Coptic Church was labelled as heresy by the Catholic Church, although you can read about the Copts and why they are upset bec Christians like you claimed they are out of mainstream Christianity.
Notwithstanding that, you need to provide me more information of
i) Who were the "two monks who greatly influenced Muhammad". In what way did they influence him. How did they influence him (textual/oral). When did they influence him. What makes you think Muhammad (pbuh) would follow a heresy teaching?
ii) The Copts did not take the apocryphal as their divine scripture. As far as I know, they follow the same 'canonical' scriptures as other Christians. What makes you so sure that the 'two monks' followed the Arabic Gospel of Infancy? Do you have any evidence (writings of Copts/other Christians) which claimed that they followed this scripture? Let me know please.
salam