"We talk about drugs a lot," Parker told PEOPLE Tuesday in New York City at the Love Heals 2014 gala to benefit the Alison Gertz Foundation for AIDS Education. "I really hate drugs, and I was always the person where that was my thing: Mary-Louise doesn't do drugs."
The actress, 49, said she keeps an open dialogue with son William Atticus, 10, whose father is Billy Crudup, and daughter Caroline Aberash, 7, whom she adopted from Ethiopia in 2007.
"I'm very afraid of drugs and very afraid of what happens especially to people who have particular biochemistry that is susceptible to addiction, which runs in my family. So we talk about it. We talk about everything," Parker said.
Not that she's a complete square.
"I tell them, 'You will never get in trouble if you're drunk and you call me and ask me to pick you up at a friend's. You do not get grounded. But if you come home in a car with someone who's [drunk and] driving or if you drive drunk …' "
Being a mom of two also guides her toward certain charities, including Love Heals, which honors the late Alison Gertz, who died of AIDS in 1992.
Parker said the charity reminds youngsters that there is still an ongoing battle.
"To many younger kids, [AIDS] is like a disease you can cure, like hepatitis – one you can get a vaccine for or fix it with a cocktail," the actress explained. "They didn't watch all their friends die [like my generation]."
She also looks to her own son as a reason to help kids across the world.
"I'm also having a raffle for my charity [Hope North Uganda] that rehabilitates escaped child soldiers in Uganda," she said, noting that the winner will be flown to L.A. and gets to bake brownies with the cast of Weeds. "I have a 10-year-old boy, and a 10-year-old boy is a 10-year-old boy. Just because he lives on another continent doesn't mean he doesn't have the same heart and the same soul and the same sensitivity, and shouldn't have the same chance at a life."
"People don't understand 30,000 children have been abducted," Parker explained. "There are no Amber Alerts in Uganda."