Lifting your parents up in my prayers right now. We were in AZ in 2000; stayed in Sedona, and there was a small brush fire at the State Park nearby with the natural water slide, I can't remember the name of it right now. And we saw a big one going and coming on a day trip to the Grand Canyon. That year there were lots of them because it had been very dry.
I have been to Slide Rock many times. It used to be a simple roadside pulloff, that has now been turned into a full-fledged State Park with parking lots, restrooms, concessions, etc. Not quite the same.