Right, switching can be slow so it's not a big deal. That leaves automotive transients including EFT, those various contact-switching surges, and load dump. How many of them do you want to support? The faster and higher impedance ones will easily be met with filtering and a small TVS (maybe even relying on MOSFET avalanche alone, though I wouldn't recommend it), and that basically leaves load dump.
Do check that it responds quickly enough to handle reversal; a mechanical connection is quite fast (nanoseconds). Likely both NMOS will be off initially (assuming time given between turning off in the forward direction, not a sudden reversal from normal operation*) so it's just down to drain capacitance, which should charge fairly quickly, and maybe provide some damping or clamping to deal with possible ringing.
*Wait, is there a transient that does that, full reversal from normal operation? I forget... That would be the limiting case if so -- whatever rise time is specified.
Tim