ashlee-simpson-evan-ross-als

Parents-to-be Ashlee Simpson and Evan Ross enjoyed a co-ed baby shower on Sunday (June 7) at sister Jessica Simpson‘s LA-based home.

Surrounded by 65 guests, Simpson, 30, and Ross, 26, celebrated their daughter on-the-way.

“It was beautiful weather and her house was the perfect setting … so gorgeous,” a guest tells PEOPLE, who adds that Simpson’s newly-engaged mom Tina helped arrange the event.

“It was very chill and almost like just a get-together than a traditional shower,” the insider adds. “It wasn’t focused on games [and was] more like a big party.”

The mom-to-be “looked gorgeous” in a “super flowy, Bohemian-style” ensemble. “Everyone was talking about Tina’s engagement and about her ring. She seems really happy,” adds the source.

Both Jessica and Evan Instagrammed some photos from the afternoon soirée.

Simpson is already mom to son Bronx Mowgli, 6, with ex-husband Pete Wentz. This will be the first child for the singer and second husband.

View Slideshow »»

ashlee-simpson-baby-shower-2
ashlee-simpson-baby-shower

View All Photos »»