No trail from rim to the river that I've seen is going to be very reasonable for carrying kayaks and gear down, if that is what you were thinking. If you are taking rafts or something and wanted to just have them hike themselves down and pick them up there may be some options. The Maze section, which contains the Doll House and access to Spanish Bottom, is not a reasonable option because the road to get there is some thing like 80 miles of dirt and serious 4x4, taking a day to get there and back. If you look at canyonlands there are three sections divided by the rivers: the Maze (W), Needles(E), and Island in the Sky (N). Needles and Island in the Sky have more reasonable access, and could be reached with less of a diversion on your shuttle if you're going back to Moab afterwards. Although I don't know the specifics, there are som hiking trails and/or backcountry routes down to the river(s) from each. I would look for a Hiking Canyonlands book or possibly websites if that is what you are after.