2010 Lexus RX 350 AWD - Driving on the beach

Hi! We take our Mercury Mountaineer to Outerbanks beaches and drive down to the shore by letting air out (from 35 to 20 PSI) and putting it into 4W-high. We need to replace this car and are thinking of buying a 2010 Lexus RX350 AWD. Can we safely drive this car on the beach? How does the 2010’s new AWD Lock mode really work? We are of the impression that when engaged, the rear driveline is locked to the front and that this state is maintained until you either put on the brakes, exceed 25mph or disengage it. In other words, that it acts pretty much like a true SUV’s 4WD-high. Have we got this wrong?