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.
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