Experience with Oath Ceremony in Islip, NY
I had my oath ceremony there a few months back. Family and friends are allowed in but make sure not to bring noisy kids with you because they may kick out noisy kids. Your "entourage" won't be allowed to sit with you though as they will be told to sit down either way in the back or where the jury usually sits.
They will give you a package with a few things in. I remember there was a passport application, a congratulation letter from President Obama, a brochure about voting, a copy of the oath and the lyrics of the Pledge of Allegiance which you will have to sing.