Like you, I don't like to use an insecticide to spray where I might wind up breathing residual toxins.

However, I've found that ordinary BrakeKleen spray kills the wasps instantly, as quick as a powerful wasp-killer spray, and the beauty of using BrakeKleen is that the fumes volatilize immediately without any residual order or residue -- no lingering insecticide in the vents or in the door jam. It kills by literally rapidly dissolving its way through the chitin exoskeleton and destroying the tissues within.

Also, the solvent is harmless to most of the car -- only the car's paint's wax protection will be affected, but that's true of a wasp spray as well. Just rewax the finish afterwards.

As Klaus suggested, wait until after dark when the whole nest's population is together, and then you can spray them all and kill every last one of them.

Good luck.