Pete Wentz and Ashlee Simpson’s New Year’s Eve Party

Pete Wentz and Ashlee Simpson-Wentz will ring in 2009 in Vegas, baby!

The new parents—who welcomed son Bronx Mowgli last month—will host a New Year’s Eve bash at Pure nightclub at Caesar’s Palace in Las Vegas.

Wentz, 29, admits in the December issue of Details that baby Bronx was “a happy accident.”

Added the Fall Out Boy frontman: “But I think that certain things happen for a reason in your life, and maybe it was time to put the wild child in a cage.”

Hmmm…wonder if Wentz will let the wild child back out of the cage on Dec. 31?