"Well, if you must know, she was conceived in New York," he tells PEOPLE

She’s only 3 months old, but already Nick Lachey‘s daughter Brooklyn Elisabeth knows an important secret.

“I’ll come up to her and make faces and she smiles and laughs, she’s already got me wrapped around her fingers,” the 41-year-old host of VH1’s Big Morning Buzz told PEOPLE after shooting the cover of the upcoming 2015 Toys “R” Us Toy Guide for Differently Abled Kids at a New Jersey photo studio Wednesday.

“The whole daddy’s-girl thing, she’s already got me hook, line and sinker,” adds Lachey, who is working with the brand on the gift guide, an annual shopping resource for those who know and love children with special needs. (Having a brother with Asperger’s, a form of Autism, has helped Lachey understand the different ways kids can learn.)

“[Brooklyn] is the happiest baby ever,” he says. “She laughs and smiles, just the sweetest disposition.”

Already, the differences between Brooklyn and her big brother, Camden John, 2, are evident.

“Cam is a little bit more reserved and our daughter is a firecracker,” Lachey explains. “You could just tell that she’s going to have a very, very strong will and she’s going to give him a run for his money.”

Nick Lachey Toys R Us

When asked how he and wife Vanessa came up with their baby girl’s name, the new dad laughs and says, “Well, if you must know, she was conceived in New York.”

He adds, “Not in Brooklyn, per se, but we felt the Upper West Side didn’t have a good ring to it and we wanted to pay an homage to New York.”

Already the couple is enjoying Brooklyn’s sweet sleep schedule. But while she’s mostly sleeping through the night, the rare times she doesn’t, it’s Vanessa who’s usually on night duty as Lachey makes a weekly commute to N.Y.C. from the family’s homes in either Los Angeles or Cincinnati to host Big Morning Buzz.

“It’s heartbreaking,” he says of leaving his kids. “I think [Camden] recovers in 30 seconds, he’s fine. For Dad, it’s tough. The older they get, with every week it gets tougher and tougher.”

Every night while away, Lachey has a bedtime ritual with his son. “God love FaceTime,” he says. “We do our little kiss through the phone and an Eskimo kiss, that’s our little deal.”

When he’s at home, after a day hanging out doing father-son things together — like hitting the car wash — Lachey is in charge of Camden’s bedtime routine, which includes a bath followed by the doting dad singing “Sleepy Eyes,” the song he wrote and recorded for his firstborn.

“That’s our thing now,” shares Lachey. “He wants to sing it every day. I have to do one for Brooklyn now, I can’t play favorites.”

But it seems Camden is already following in his father’s musical footsteps.

“I’ll put different words to a song, like ‘Frere Jacques,’ ” he explains, laughing, as he uses the tune to sing, “Chew and swallow, chew and swallow, all your food, all your food, it is so good for you, it is so good for you, yes it’s true, yes it’s true.”

He continues, “[Camden] will take that melody and he’ll put his own, like, ‘Super Camden, Super Camden.’ And he’ll be starting to write his own and improv his own lyrics to songs. It does seem like he’s musically gifted.”

— Diane Herbst