I understand the OP's concern. Given Marriott's CS issues of late, including things like pretty much ignoring elite "guarantees", it's not out of the question that they would show up at the hotel only to be told there are no rooms available, and sorry, everything else is sold out too and the ultimate reservation guarantee doesn't apply due to the fires being a special circumstance. That being said, I'm not sure what more they can do at this point than check with Marriott and take them at their word that "your reservation will be honored" means exactly that.

How sad that, until the past year or so, I would never have even doubted Marriott to stand up to their word. I would have defended them against any other hotel company as being the most honest, ethical, and customer-focused.