Recently I observed someone who was checking in being asked for photo ID to prove age in order to get a key to the minibar.

Lots of reasons to check this out in advance. Looking for a room at the rack rate at the last second can be extraordinarily expensive and frustrating. OP needs to know the specific policy of the specific property as of the specific date. What other properties do and don't do and what others have been able to make and not make happen is irrelevant.