If the legal adoption process completed before landing, your current COPR is invalid. Your family changed and you need to add the new member in your application before landing.
That new member will need to pass medical, police and background check and new COPR will be provided to land with all family members. Otherwise, this new child would be excluded forever from your family and you can never sponsor him/her.
But this adoption may not be recognized by IRCC/Canada since a biological parent is still alive.
Best to consult a lawyer that's familiar with international adoption and immigration.