I think you have a pretty good plan except for the batteries.
How long do you plan to be gone ?

The HV battery gets disconnected with a big relay whenever the car is OFF.
It would be better to connect a good battery tender to the 12 V (NOT a cheap trickle charger) and if you do that, no need to disconnect it.

If there is any chance at all that rodents will be nearby, put out a couple of "safety" bait stations.