Welcome to YorkieTalk. Thank you for joining our growing family of Yorkie lovers. Congratulations to the new addition to your family - can't wait to see pics.
My first suggestion about introducing the pup to your son is to not stress out. Pups are generally curious about humans and if your son has been taught how to behave around dogs then it should be a natural process. I'd have him sit down on the floor and allow the pup to introduce herself to him. I would expect that the pup will be all over him giving kisses, etc.
That said, I wouldn't leave them alone together and I wouldn't allow him to pick the pup up.