Kourtney Kardashian and Scott Disick celebrated their sons' birthdays at the happiest place on Earth!

Mason, 7, and Reign, 2 -- who were born five years apart on Dec. 14 -- were treated to a fun-filled day at Disneyland in Anaheim, California, on Wednesday. Their grandmother, Kris Jenner, was also in attendance, as well as their sister, 4-year-old Penelope, and cousin, 3-year-old North West, an eyewitness tells ET.

WATCH: Scott Disick Shares Sweet Family Photos, Calls Mason 'the Boss in My Life'

"Birthday boy," Kourtney captioned an adorable pic of little Reign, clad in black sweats, matching sneakers and a blue-and-white bomber jacket.

"My twin boys born five years apart," another post read. "Luckiest mommy in the world. Happy birthday to them. ??"

Inside the theme park, birthday boys Mason and Reign got an extra special treat -- a tray of chocolate cupcakes with red frosting and an assortment of Mickey Mouse balloons, as Kourtney documented via Snapchat.

According to the eyewitness, who spotted the group standing in line for the Indiana Jones Adventure ride, "all of the kids looked happy and excited to be there."

"Kris looked happy to be spending time with the kids," the eyewitness added. "Kourtney and Scott looked a little irritated, but it could just be because they were tired -- definitely no romance or cuteness between the two of them."

Following their fun-filled day, Kris took to Instagram to gush over her "two sweet boys."

WATCH: Kardashian Family Celebrates 'Precious Angels' Mason and Reign's Birthdays

"Our precious angels Mason and Reign," she wrote. "I love you more than words can say. ?? #myheart."

Hear more birthday messages from the family in the video below.