I did the smaller tour on July 20 and it was a great time. I've done the full tour before, but this one was a good mix of views and kayaking for a beginner. The kayaks we were assigned had rudders, which made the tour so much easier. The guides were great and very knowledgeable about the river and anything you needed to know about kayaking.
We bought some cheap ($10) water shoes on amazon, but I guess any kind of sandals/shoes would work, as you didn't have to spend too much time wading in the water (getting into and out of kayak mainly). The lunch was pretty good (Jason's Deli?) during our break and there were spots where people could jump off rocks into the river (water is very cold though...). The day we went was overcast, but still fun (a sunny day would be much better). This is something you should definitely try when in Vegas!