The SFO folks are really nice if you ask for what you want. When there were no SUVs on the aisle, I asked and they brought me one. Another time, I arrived with an SUV reservation, family and lots of luggage. They said "wow, you've got a lot of stuff, let's get you something big" and brought out a large SUV.

Sat at 2pm is kind of a bad time to pick up a car, as a lot of nice cars will be out for weekend rentals. Get a reasonable reservation and prepare to ask nicely.

If it was me, I'd probably get the mid-size SUV reservation and ask for a big SUV. I wouldn't get the premium reservation.