Combination question: Hertz at LAX Marriott, upgrading to 7-passenger vehicle

I travel from SFO to LAX fairly often—have rented from Hertz LAX several times and have stayed at the LAX Marriott several times. But I’ve never rented from the Hertz counter at the LAX Marriott. If I’m headed to the Marriott anyway, picking up a car there might be more convenient than boarding the separate rental car shuttle first, plus going off-site saves about $20 worth of fees for three-day rental.

I’d assume the fleet is very limited, but does anyone have experiences at the LAX Marriott Hertz to share?

Also, I’ll be in LA next month where family from across the country will be converging for a graduation, and this is one instance where having a six- or seven-passanger vehicle might be a benefit. But for the dates I’m checking, a minivan is more than three times the rate of a full-size—with seven-passenger SUVs being even more. Is there any way I could upgrade into a minivan for less? Is this a case where using points would make more sense? At these prices, we’d be far better off with two sedans.

And combining the second question with the first: I assume if I was trying to do any sort of upgrading to a minivan, I’d be far better off at LAX than the Marriott counter.