We were also there over Labor Day last year, and we also thought the parks were dead. The water rides are slammed because it's approximately a billion degrees, but other than that, we did all of our favorites multiple times, including TSM with waits of 20-25 minutes in the afternoon.
Frankly, misting fans and Frog's Togs just aren't enough. Pretty much the only way to effectively deal with the heat is to escape from it. We did RD-early afternoon, and then a long break spent in the pool, and then back for evening once the sun wasn't so direct. I can't even begin to explain how hot the sun is at mid-day. We decided to suck it up and wanted one last ride on Splash before break, and I knew the line for it would be short leading up to FoF, so we hopped in line at 2:45ish and got to see part of the parade while on the ride. But our plan was sorta a fail, because then we got off the ride and couldn't get out of Frontierland until the parade had passed. We were standing there, dripping sweat within minutes, as we watched the parade from the walkway in front of the Splash drop. It was nice to see the parade, but OMG we were so, so hot in the sun. A pool has never, ever felt as good as it did that afternoon.