Tiggy - we were lucky in that our trip was comprised of three couples. The girls left two vehicles at the takeout (which I consider pretty secure because of its isolation) and drove one back to park at Valle's. The boys got to rig and drink coffee while the girls did the long drive. Sounds like the shuttle is your solution.
Looks like you'll have more water than we did. Our run was 2000ish, which was enough to cover most of the rocks in Govt. Rapid. Our last day from Grand Gulch to the takeout involved a lot of sandbar dodging/dragging, but we lucked out on the wind.
Flow projection courtesy of Rivermanryan: SAN JUAN - BLUFF, NR (BFFU1)