Unfortunately, that's memorial day weekend so rates are likely to be higher than typical. Have you tried AutoSlash? That's your best bet, in leiu of adding every discount code and trying yourself. I'd also give Costco codes a try, as they're usually pretty good.

Also, what about taking a taxi/Uber to an off-airport property? Might save quite a bit, especially in taxes/fees.

Finally: after you book, keep searching. Rates often change substantially as dates draw near.