Based on past experience (high school out of town field trip to Florida many years ago where none of the students, except myself had credit cards), when on a pre-paid stay at a hotel, even if you don't provide a credit card (authorization) and/or a cash deposit when checking-in, the hotel in theory can't deny you from staying there.

All that would happen is that they would prevent you from using any incidentals that are charged to the room. For example, none of the phones in the rooms for the student's had the capability of calling outside the hotel (they all had to use the payphone in the lobby to call home - this was during a time when cell phones were not common among high school students), the minibars were locked, pay per-view movies disabled, and when one of my classmates tried to order room service, he was told that he had to pay cash to the server directly as they can't charge the room.

Myself on the other hand, had a supplementary credit card from my parents and went to the front desk to ask them to swipe it for an authorization. This allowed me to use the phone in my room to call home, order pay-per-view movies, and charge purchases from the hotel gift shop to the room.