James Tupper and Anne Heche
05/13/2009 at 07:00 PM EDT
Taking a break from Daddy duty, actor James Tupper joked that fathering his newborn son
, Atlas, with Anne Heche has been exhausting.
"It's a bit like having an unreasonable employer," he told PEOPLE. "He doesn't give breaks."
Tupper, who is also step-dad to Heche's son Homer, 7, from her marriage to Coley Lafoon, admits that as babies go, Atlas is very well-behaved. "I always imagine babies crying," he says. "He doesn't really. He's very sweet. He's in a warm bath of love and attention."
From the sounds of it, Atlas will soon be living up to his name: NBC announced that it's ordering more episodes of Tupper's pilot Mercy,
, a medical dramedy (also starring Taylor Schilling, Michelle Trachtenberg, and Jamie Lee Kirchner), which will film in New York.
"He will be a bicoastal baby," says Tupper, who adds that the double blessing of a blossoming family and a new TV series "is like being awake in a dream."
So, how does Heche feel about her partner going bicoastal? "She's taking it a day at a time," he says.
In the meantime, she's got a full – and musical – home. Tupper, who plays the guitar, surprised Anne on Mother's Day. "I bought Anne an upright piano, and some lessons," Tupper says. "Her dad was a piano player. She plays, and I got her some lessons."