12/30/2012 at 10:50 AM EST
is sending 2012 off with a bang!
The 28-year-old showed off her svelte figure in a tiny bikini as she splashed along the shores of Oahu, Hawaii on Saturday.
The singer and son Bronx
(with Pete Wentz) joined pregnant big sister Jessica
, her fiancé Eric Johnson
and 7-month-old niece Maxwell Drew
for a Hawaiian holiday.
Ashlee – who recently split
from Boardwalk Empire
actor Vincent Piazza after a year and a half of dating – smiled as she held hands with Bronx, 4.
This holiday season has been all about family for the Simpson clan. Tina Simpson – who filed for divorce
from husband of 34 years, Joe Simpson, in October – also joined the girls in Hawaii