"We are taking a family trip for Thanksgiving," Rancic told ABC News in promotion of Small Business Big Game. "We are going to go with a few other couples and their kids, we're going to Tahiti, which I've never been. We are going to spend eight days on the beaches and I'm going to teach him to swim."
Rancic said as a father, this milestone is something he'll cherish.
"When he started walking, let me tell you, I was freaking out," he said. "It was just so cool, to be able to see him scoot around the house and he picked it up so quickly, like overnight! He runs now."
The former "Apprentice" winner, 42, said he and his wife have their hands full since little Duke loves to get into everything now and see how it works.
"He loves opening and closing cabinets, he fascinated by how cabinets and drawers work," he said laughing. "We were on a flight the other day and the poor people around us. He spent one hour opening and closing the overhead compartments."
The "Giuliana & Bill" stars both have large families that he said are so happy around the holidays because they get to see and play with his adorable son.
"I have eight nieces and nephews on my side and Giuliana has six on her side," Rancic added. "His cousins, they just love him. My sister has three boys, so we bring him over to her house and they are wrestling. He's all-boy, he just loves hanging with his older cousins."
Note: There's still two days left to vote for the four finalists in the Small Business Big Game competition, where one small business will win a 30-second Super Bowl ad - Vote Here.