Stephanie D. Kleinman
“I’m so excited to have a son,” Simpson, 32, tells PEOPLE exclusively. “He got all these cute vintage cars and I got a lot of little leather jackets I can’t wait to try out!”
The Fashion Star mentor’s 11-month-old daughter Maxwell Drew got excited too. “She was taking over some of her little brother’s gifts!” says Simpson.
The mom-to-be — whose fiancé Eric Johnson later joined the celebration hosted by Simpson’s mom Tina and attended by sister Ashlee — celebrated her son’s impending arrival with a Tom Sawyer-themed bash created by celebrity event planner Mindy Weiss, who gives PEOPLE an exclusive private tour of the party below.
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The menu included treats for kids (a grilled cheese station!) and Southern comfort food.
“I always love some fried chicken,” says Simpson, who has been working out three times a week with trainer Harley Pasternak. “This pregnancy I’m active. I’ve only gained half of what I gained in my first pregnancy.”
For more of our exclusive interview and photos from the big day, check out the new issue of PEOPLE, on newsstands Friday.
— Aili Nahas