I'm thinking of possibly quitting my nannying job without warning on friday
Why do you want to quit being a nanny so suddenly?
I just feel my job is not needed
Since this is someone's childcare we're talking about here, I think it'd be better if you gave notice before quitting.  You don't want to leave the child without someone to take care of him, do you?
I think it'd better if I just disappear and let the kid worry about where I am or if he will have anyone to take care of him. It's not like he can tell anyone or go to a child protective agency since he's just a kid.
Taking care of a child is a very important and special job. At least let the parents know what is up. Give them a simple text or call so they can arrange ahead of time.