"I went there on our three-year wedding anniversary," she tells Jane magazine for its November issue. "He stayed home"
Simpson was part of a travel contingent representing Operation Smile, a not-for-profit, volunteer medical services organization that provides reconstructive facial surgery to indigent children in remote areas.
Although Simpson and Lachey had both been presented with the organization's Universal Smile Award at a Los Angeles Gala, Simpson ended up traveling to Nakuru, Kenya, with hairdresser Ken Paves, friend Cacee Cobb and her manger-father, Joe Simpson.
Once in Africa, according to the official Operation Smile Web site, Simpson aided the volunteer team with the medical evaluations of more than 280 patients and gave out gifts and spread cheer to the kids as they awaited their medical procedures.
She and Lachey separated in November 2005.