When to tell everyone?!

Since recently finding out I'm pregnant, I've begun feeling anxious about when is the "right time" to tell everyone...
I am 7 weeks and 3 days
I only started a new job 4 weeks ago so I'm worried about telling my manager as I'm still finding my feet in the new role
My little boy who is 5 is desperate for younger siblings and I've been so tempted to tell him but also would find it so difficult to then tell him if we lost the baby. I'm certain I want him to know before everyone else in the family
Additionally for me to worry about, I have a friend who has been ttc for over 2 years and suffered 1 mmc. She is a very close friend who has openly said she doesn't know how she'd cope if anyone else fell pregnant before her. I don't want to lose her as a friend but need to tell her at some point. 
So all this stressing is having a bit of a negative feeling around my pregnancy. I really want to only have positive vibes about the baby and the future :) any advice would be lovely.