The actress shares Violet, 18, Seraphina, 15, and Samuel, 12, with ex Ben Affleck

Jennifer Garner is happy with where her kids are.

In this week’s issue of PEOPLE, the actress, 51, shared that her kids Violet, 18, Seraphina, 15, and Samuel 12, are giving her the most joy as she gets ready to celebrate her 52nd birthday. “They’re really solid right now,” says the star and Neutrogena brand ambassador.

“I’m just watching them in this new phase of life where they’re figuring out who they’re going to be and what they’re going to study. And I’m so interested in them. All the time, I’m interested in everything about them.”

Asked if it’s difficult to let her kids make their own decisions, Garner admits it’s “so hard.”

Jennifer Garner and daughter Violet. NATHAN HOWARD/GETTY

“I mean, my parents did too, and I’m so amazed by that. I have a really hard time not saying, ‘This is what I see you as,’ and ‘I think you should,’ ” she says. “I really have to sit on my hands.”

Garner shares her three children with ex Ben Affleck.

In November, the mom of three appeared on Live with Kelly & Mark, chatting with co-hosts Mark Consuelos and Kelly Ripa about how her child Violet is starting college tours.

Jennifer Garner and son Samuel. ALLEN BEREZOVSKY/GETTY

“We hear you’re about to have an adult in your household?” Consuelos said to Garner.

“I am. I’m about to have an adult,” Garner responded. “Three days. I’m three days from my eldest turning 18. Can you guys believe that?”

Noting that it’s “exciting,” Garner added that Violet was taking charge of her own college process.

“It is exciting,” the actress affirmed. “I can see the stress — even though the excitement and stress go hand in hand. But she’s handling it like a champ and she’s totally in charge. I’m not having to say, ‘Are you doing this, are you doing this?’ She’s a self-starter. And I’m just proud of her no matter what.”