Melissa Joan Hart Shares Why It's So 'Upsetting' To Watch Her 3 Boys Get Older

Melissa Joan Hart is having a hard time watching her sons grow into men, especially now that her oldest is getting behind the wheel.

"They're getting huge," the 45-year-old actress told PEOPLE at Steven Tyler's Fourth Annual Grammy Awards Viewing Party benefiting Janie's Fund in Hollywood on April 3. "My oldest is driving and it's really upsetting."

The mother to sons Mason, 16, Braydon, 14 and Tucker, 9, has found the silver lining in her fears since Mason can now help shuttle his brothers around. "It's great because it's super helpful."

As if one license wasn't enough for the former Sabrina the Teenage Witch star to worry about, she now has to stress over two!

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"He's a pilot also, so he flies planes," Hart explains. "I know he has a respect for engineering and machinery. So that helps. The younger two I'm more afraid of driving. But it's just a loss of — It's a loss of their childhood when they start driving, which is weird."

Watching her son operate machinery hasn't been the only awkward moment in her household! Hart and her husband of almost 20 years, Mark Wilkerson, are beginning to have the birds and the bees conversations with her kids and they're all handling it differently.

"The oldest one wants to know nothing," Hart explains. "He's like, 'Stop, I don't want to know.' The middle one's like, 'Tell me a little. That's gross. Okay. Stop,' and the little one is like, 'Tell me everything. What's a period?' "

The actress knows it probably isn't easy for her boys to come to their mom for advice on such personal matters. Despite the awkwardness, she lets them know she's always there when they're ready to talk and won't embarrass them.

"I want them to feel like they can come to me with questions," she says. "But I also don't feel like I'm wanting them to feel like, 'Oh my God, mom,' close the ears and shy away because that's a little creepy too if your mom tells you too much detail."

Although it's been challenging to see her boys grow up in front of her eyes so quickly, Hart is pleased to see Mason focusing on himself rather than girls.

"I like that," Hart shares, noting her son isn't that interested in dating at the moment. "He's sort of navigating it now. But he wants to focus on football, so he doesn't want to anything to distract him from that. That's the way my husband grew up as well. I don't know if it's hereditary or he saw it from dad. They also have big cousins that are teenagers that are in [their] college years and they watch that. They kind of pay attention to them and learn from them."