I think it'll be pushing it a little.
By the time you get out of the show it'll probably at least around 8:30 if not later especially with the crowds. And then you can either walk it or wait for the boat - unless you have a car. The boat will take you longer sometimes because it stops at Swan/Dolphin, Beach/Yacht and then BW. If you are still thinking of doing the boat instead of walking (it's a good hike over to FF), get off at S/D and then walk to FF. It's faster than waiting for the boat to go all the way over the BW.
Have fun!