Pregnant Mila Kunis and Ashton Kutcher were "very playful" during an ice cream date on Kunis' 31st birthday in L.A. on Thursday, Aug. 14 Credit: National Photo Group

A treat for his sweet! Ashton Kutcher accompanied fiancee Mila Kunis for an ice cream date on her 31st birthday in L.A. on Thursday, Aug. 14.

The soon-to-be parents indulged on the late-night dessert at Sweet Rose Creamery at Beverly Boulevard. Kunis wore a cleavage-baring maxi dress that showed off her growing baby bump during the outing.

"They were very playful, grooving to the music playing in the shop, and clearly just really focused on and into each other!" an eyewitness tells Us Weekly of the couple.

"He was totally doting on her — rubbing her belly and opening the door for her," the onlooker adds. "They looked so in love and were acting goofy!"

Earlier in the day, Kunis stepped out to attend a maternity yoga class in L.A. She donned black short shorts, a fitted spaghetti strap tank top and accessorized with flip flops and aviator sunglasses.