The stay would be Sunday night with my brand new wife
The hotel was indeed the old Hyatt. The former Renaissance is now the Ramada. craz, the former Hyatt is now the Dan Jerusalem, not Dan Regency. Dan has 4 hotels in Jerusalem: The King David, Dan Panorama (Keren Hayesod, next to the King Solomon,) Dan Boutique (Derech Chevron, former Ariel Hotel), and Dan Jerusalem (Mount Scopus, former Hyatt).
I called the front desk and reservations and both said the same thing regarding check in. They said check out is 12:00, and only if the room hasn't been vacated yet would check-in not be until 13:00. But in general, many of their rooms are taken by groups and vacated by 08:00 they said. It still just sounds too good to be true and not worth risking, but an early check in is essential, because it would allow me to check in in the morning so after the wedding, there's no need to bother with that, AND it would allow me and my 2 friend to get ready in the room as opposed to heading back to Efrat from Jerusalem before going to the hall.