"We've never been in the business of wanting to appear perfect and pretend that there aren't cracks," Erin Foster tells PEOPLE of her family

Life under lockdown amid the coronavirus pandemic has brought about a new tradition for David Foster and his daughters Sara, Erin and Jordan: family Sundays.

Each week since lockdown began in mid-March, the family has congregated in the backyard of Erin's Los Angeles home to talk life, debate politics, share a glass of wine — and plenty of laughs.

"Her backyard has become our playground,” says David, 70, in this week's issue of PEOPLE, on newsstands Friday.

Though the family is now (literally!) closer than ever, they've had their fair share of pain to work through from their past. When Sara, 39, Erin, 37, and Jordan, 34, were kids, David divorced their mother, his second wife Rebecca Foster, in 1986 and moved in with his third wife Linda Thompson shortly after.

"I missed a lot because I didn't raise them," says David, now re-married for the fifth time, to singer-actress Katharine McPhee, 36. "The geography was really tough. That was my own doing and a regret that I have, but it was what it was and there was no changing it. So I did the best I could, which was quite imperfect at times. Plus I worked so much. I mean, I've made a pound of music in my life."

According to the girls' mom, David "lived in the studio" during their childhood.

"He was working to provide for us," Sara says. "As an adult, you realize it's impossible to be a perfect parent, and you don't realize that until you have your own kids."

RELATED VIDEO: Family Means Everything to the Fosters

Jordan makes clear though that they felt that their dad was "there always" growing up — especially to teach them invaluable life lessons. Once, Erin got caught smoking a cigarette and David made her write a report about it.

"I had to give the report to all my teachers," Erin says. "I had to go to the local doctor's office and learn about how bad it was for me. I've had a couple of drunk cigarettes in my day, but I never became a smoker."

Sara says he also instilled in them the message: "I'm rich, you're poor."

"If I knew at 19 while I was living in Paris, going on castings for these like s— catalogs, that there was a trust fund waiting for me in two years, I would not have been doing that," she says. "Absolutely not. So I appreciate that sort of value system that was put in play early on because I work hard, and I love what we do. I'm so grateful for that work ethic."

David Foster photographed with his daughters Erin, Sara, and Jordan in Los Angeles, CA, on 6/26/2020.
Erin, David, Jordan and Sara Foster
| Credit: Anais & Dax

Even though it was an "imperfect situation" that she and her sisters lived in a separate house than their dad growing up, Sara says they've been able to develop a "great relationship as adults."

"To be able to have my dad as a sounding board, someone to go to for advice, someone who my daughters [Valentina, 9, and Josephine, 4] are obsessed with, I'm so grateful for," she says. "He calls us every day. It's a little annoying sometimes. I pick up every other day. I think we've worked really hard to get here."

A new documentary about David's life and career, David Foster: Off the Record, which will be released on Netflix Wednesday, propelled conversations about their relationships even further.

"We've gotten to a point in our relationship with each other and in our adult lives where we want to be able to confront each other about things and have conversations that are open and honest," Erin says. "Regardless of if you're in the spotlight or not, it's what every family should be doing, because then you can put it behind you. Our narrative is that we're all on the same side and we've all been mad at each other. We've all forgiven each other. And we're a family just like any other family."

Says David: "I used to think, 'Well my daughters aren't pregnant at 14, and they don't do drugs, I did my job.' It's obviously more complicated than that."

Though David admits it was "hard to watch people opening up" in the documentary, he "wanted it to be [director] Barry Avrich's film."

"So for better or worse, I let him roll with it," he says. "Otherwise it becomes a puff piece about your work and like, 'Wow, what an amazing guy.' But I'm sometimes not an amazing guy, and that came through loud and clear."

Jordan says to David's credit, he told them all "to be really honest."

"I said to you, 'Is there anything you don't want me to touch on?'" she says. "You were like, 'Say anything you want.'"

In addition to their family life, the documentary delves into David's successful music career and features interviews with some of his biggest collaborators — including Michael Bublé (whom he discovered), Lionel RichieQuincy Jones, Chicago's James Pankow, Barbra Streisand and Céline Dion — as they talk about his musical genius. It also touches on his reality TV stint on the Real Housewives of Beverly Hills, which was filmed before his divorce from ex-wife Yolanda Hadid.

"I'm at peace with it," David says. "[My daughters] were smart enough to not be part of it. But I have no regrets. I always said, 'Look, I don't think X, Y or Z is going to go, "I saw him on that show, and there's no way I want him."' I felt that I was immune from that and I still feel that way, even if it's true or not."

David Foster
David Foster
| Credit: Jim Jordan

While their family story might seem made for reality TV, Erin says they "won't be involved in any of that stuff."

Adds Sara: "The goal is to stay off reality TV."

With the documentary, Erin says she and her family are proud to expose their vulnerable sides.

"We've never been in the business of wanting to appear perfect and pretend that there aren't cracks because that's unrealistic for anybody," she says. "It's really easy to think that someone else's family is perfect or someone else's life is perfect. None of our lives are perfect. Our family's not perfect. But that doesn't mean that it's not great."

For more from David Foster and his daughters on their unique family journey, pick up the latest issue of PEOPLE, on newsstands Friday.