The family of three headed out for a hike Sunday, reported E!online.
"Daddy and son Sunday hike," Duff posted along with a photograph of her estranged husband and their 22-month-old tot walking on a trail.
The 26-year-old actress made her first red carpet appearance post-split at the 2014 Grammy Weekend Reception party in West Hollywood, California.
While she kept mum on the break-up at the event, she seemed to be in great spirits while chatting and laughing with friends before Lorde performed for guests.