The party's not over for Haley Cavinder and Jake Ferguson -- the couple's bachelor-bachelorette celebration went to overtime in Vegas, where Haley and her twin, Hanna, turned heads in teeny bikinis at one of the hottest dayclubs in Sin City!

Haley and the Dallas Cowboys tight end got engaged in April 2025 and kicked off their bachelor/ette festivities earlier this month with family and friends, starting with a trip to the Bahamas.

They've since moved on to Vegas for the grand reopening of the famed Marquee Dayclub ... where the Cavinder twins showed up over the weekend, and stole the spotlight, wearing barely-there swimsuits.

Haley rocked a pearl-detailed yellow two-piece, while Hanna turned up the heat in a zebra-stripped bikini paired with a lace bottom cover-up.

The twins -- former Miami Hurricanes basketball stars -- were accompanied by Ferguson, his dad, Cowboys quarterback Will Grier, his wife, and Dallas Cowboys cheerleader Haley Anderson.

We're told the crew enjoyed the dayclub in the venue's large cabana and sipped on Casa Dragones, Coors Light, and table-side ranch water specialty cocktails.

We're also told NBA star Jimmy Butler was in attendance for the Marquee extravaganza -- hanging out with the DJ and feasting on premium food and beverages ... as DJ Martin Garrix provided tunes.

Now that's how you do a Vegas weekend!