Maci Bookout's son Bentley is growing up fast!

Turning four years old on Oct. 27, Bentley, the Teen Mom star's son with ex Ryan Edwards was feted with a cowboy-themed bash that would make any other boy his age jealous.

PHOTOS: A-list kid birthday party blowouts

"My little cowboy turned four today!! such an awesome day!" Tennessee-based Bookout, 21, tweeted on her son's big day, posting a pic of him dressed up in an adorable checkered shirt, straw hat and red bandana. "He is my perfect world."

Maci Bookout and son Bentley
Credit: Instagram

On the agenda for Bentley's big bash: Horse rides, a petting zoo, and -- breaking with the cowboy theme -- a motorcross-inspired birthday cake!

Welcoming Bentley in 2008 with ex Edwards, Bookout calls her son's birthday celebrations one of the toughest times to be a single mom, because she has to share custody of him with his dad.

VIDEO: Maci shares Bentley's latest milestones

"Birthdays and holidays are the hardest because we have to share him, but coparenting with Ryan is getting better," Bookout told Us Weekly in August.