The actress, 41, spoke at the New York Society for the Prevention of Cruelty to Children annual spring lunch on Tuesday.
"She is a champion for children through the United Nations," a source tells PEOPLE.
At the event, Barrymore read a chapter from her book Wildflower titled "Africa", which told the story of her time working with children in Africa. Before starting, she warned the crowd that she might become emotional while reading.
"If I break down during this story, you will understand, I will just turn it into laughter and you men will think we're crazy," she said. "We are, but it's that craziness that actually evolves into compassion, and that's what's so beautiful about women."
As she began, Barrymore became emotional when she described hugging a girl with AIDS to whom she had sent money for help after a previous trip. The actress put her hand on her chest as she fought back tears while reading.
She avoided mentioning Kopelman (skipping over portions of the book excerpt that included him) and didn't bring up her divorce.
Barrymore and Kopelman confirmed their split after nearly four years of marriage on April 2, and her appearance comes as the two begin to work out the details of their divorce.
In an exclusive statement to PEOPLE, Barrymore and Kopelman said their children, Olive, 3, and Frankie, 1, will be their "first priority" moving forward, and those who know them best do not expect a custody battle.
Reporting by JEFFREY SLONIM