Watching Harry Potter AndThe Prizoner Of Azkaban

Dumbledore gets a strange letter saying how ‘the marauders, Snape, Wealseys, Mcgonagall, himself, Poppy, and Hagrid all will watch the life in third year (and possible more if i want heheheheh) of a student. How will Lily and James react to having a son! How will Evryone react to Harry Potter. Will Snape get through the movie without breaking something (most likely not)