Well plan on it being very cool that time of year. We did it last year in September and it was cold in the evenings. Be sure to look up the Burr Trail in Southwest Utah, it is incredible and it is dirt, but gravel and passable for the most part. Try to hit hells backbone while your out there, that is also in Utah in the general vicinity. Since you are so close to Zion and Bryce, hike those if you can, well worth taking a day to hike those.
On your way back you can hit Sedona AZ awesome views and ride, Moki dugway for a little dirt riding, there is also the Coronado trail if you have time to hit South-eastern Arizona. Colorado is incredible as well, but you will not have time. At the very least include 550 through Durango to Ouray, nice if there is no snow on the roads.
happy trails, wish I was going back.