My only concern would be the ambient temperature along the trip. If you're doing it in the winter, if it's going to be below freezing for some of the trip the car MAY expend some energy trying to keep the pack at a reasonable temperature.
I think the official temperature it kicks in the heaters at is -5°F. This is why they encourage dealers and customers in colder climates to keep the cars plugged in (or to do routine checks). I've had a few instances where I've seen an 8% drain over the day when parked at work outside when it's been bitter cold out (around -13°F, which happens a week or two a year here at times).
If it's above freezing most or all of the trip, you'll likely only see a few percentage points lost per week at best. The 12V becomes the next larger concern, as others have noted. But even that should be fine for a week or two on it's own if it's topped off before the trip starts.
