The singer and her fiancé posted photos from the celebratory affair

Credit: Courtesy Ashlee Simpson

Second time’s the charm!

Ashlee Simpson is getting ready to wed again, and the pop singer announced on Twitter Wednesday night that she had a great time celebrating her engagement to her boyfriend of nine months, actor and musician Evan Ross.

“What an amazing engagement party with all of our loved ones!” Simpson, 29, Tweeted. “We gettin’ married :).”

The popster also posted a Twitpic showing the two festively decked out – she in a white feather headdress, he in a fuzzy overcoat – as they lean in for a sweet kiss.

A source tells PEOPLE that the party was held at the home of the bride-to-be’s mom, Tina Simpson, and the mood veered boho-chic – decor included dream catchers and teepees. A live band played for guests, which included the couple’s entire families.

Ashlee’s 5-year-old son, Bronx Mowgli – from her first marriage, to Fall Out Boy bassist Pete Wentz – also came up with the idea for guests to sport silver tribal markings, the source adds.

Her fiancé, who is the son of music legend Diana Ross, also shared his own snapshots from the fête, which – based on his Instagram posts – also served as a great chance to wish his famous mom a happy birthday. (She turned 70 on Wednesday.)

RELATED: Jessica Simpson Wears Sexy Plunging Mini to Sister Ashlee’s Engagement Party

“What an amazing engagement party. Love you,” he captioned one image dedicated to his bride-to-be, while another – showing him sitting with his mom – read: “Happy birthday mom I love you sooooo much.”

On Jan. 13, Simpson and Ross announced their engagement with a Tweet that said, “My baby love and I are ENGAGED!!! Hallelujah Hawaii!!”