We used the Millburn P.O. I think you need to make an appointment and bring pictures.
Millburn and Livingston do it with an appointment (at least on weekends). But Short Hills can do it without an appointment, even on Saturdays. They don't take pictures.
If you need everything including photos in one place, on weekends, without an appointment, then it is downtown Newark or Clifton.
(we just took the kids to Short Hills for renewals a couple of weeks ago)
We just did photos and application in Summit. They have appointments.
Now that our brand new post office no longer offer this service, where do you go to renew the little people's passports?