My wife and I booked a Thursday afternoon SUP trip online on the Monday beforehand. Abbey called the afternoon before and left a confirmation message. She picked us up right from our hotel and drove us to the launch point. After a few minutes of wobbling around on the board, we started to get the hang of it and took off down river. The next couple hours were a fantastic mix of relaxed paddling and a couple exciting runs through the rapids (its a lot easier going in on your knees).
The folks at Paddle Moab absolutely know what they're doing and took care of us fantastically (there were even snacks after the trip!). They should be on top of your list as a way to get out of the heat and experience the river up close and personal.