Within hours of trying to reach her husband on his cell phone at home in Yakima, Washington, Brooke Cox knew that something was wrong. It wasn't like Mark Cox, an attorney, not to pick up or call back.

"I called his work, I called our friends - nobody had seen him that day," says Brooke, 38, who was visiting her parents in southern Utah with her five children on that July day in 2011. "So I asked a neighbor to call 911, then go and check on him. I had a very bad feeling."

When her friend looked in the front window and said that she saw Mark lying unresponsive on the sofa, Brooke started trembling. Paramedics who broke into the house confirmed the bad news: Mark, 34, was dead. Tests revealed that he'd died of a brain aneurysm sometime during the night.

Sobbing, Brooke gathered her children in a group hug. "I was grateful that they hadn't been there to experience the trauma of it," she tells PEOPLE. "None of them had to find him like that on the couch. It was a blessing to be away and with family. I hugged and hugged my kids and didn't want to let go. I felt that my arms couldn't be long enough."

About nine months after her husband's funeral, Brooke attended a conference for young widows and widowers that focused on how to get through the different stages of grieving.

"I thought, 'I need to do something like this for my kids,' " she says, "but when I got on the Internet, I couldn't find anything. There were camps and workshops for people who had lost loved ones to cancer or suicide, but there was nothing specific to what my children needed. So I thought, 'You know what? I'm going to do this.' "

Today, her charity, which she started in April 2014, puts on a yearly summer camp for children who have lost a parent. This year's camp will be held Aug. 1 in Salt Lake City, Utah, not far from Saratoga Springs, where Brooke and her children now live.

With workshops on grieving geared differently for toddlers and teenagers, outdoor games and a barbecue, "It's a fun way to let kids know that they can overcome," says Brooke, a stay-at-home mom to Kaleb, 15, Colin, 13, Chase, 11, Abbey, 9, and Eli, 5. Since the program began, she has helped more than 300 children in her husband's name.

"You can't imagine what some of these kids have gone through," she tells PEOPLE. "They've lost parents to cancer, car accidents, even murder. At our camp, they know they can open up and be with other kids who understand. They've all felt the pain of losing somebody they love."

Brooke, who was married to Mark for 12 years, misses him daily, especially when her youngest children need somebody to wrestle with or cuddle with at bedtime.