They're there for a Play(Double)Date

Morgan and Jason didn't come to the playground just to play.

They were there to meet someone. They met at least once a week, sometimes at each other's houses or at a restaurant, and this week it was at the playground.

While Jason would go on regular dates, hiring a babysitter to look after Morgan since you don't leave your baby home alone, he would regularly bring her with him because his new paramour had a baby of their own. A part of Morgan was jealous that there was someone else taking time with daddy, but her grown-up self was happy for him.