"Certainly, the children enjoy these things, but I think also they make a lot of the adults who give money to the foundation and the parents of the child feel like they can do something when everything else seems hopeless," he said.
For the families, the final wish provides memories.
"One of the things that's very important to families who might lose a child is to know that they've done everything that they can for their child," Koocher said. "Even if they lose the child, they've preserved some positive memories."
Other national programs support the dying wishes of children. Caps for Kids helps cancer patients get an autographed hat from their hero -- sometimes it's Mickey Mouse and other times it's Hannah Montana. The program coincides with chemotherapy, which typically robs children of their hair.
At Children's Medical Center in Dallas, where Jayla and Jose were treated, pre-teen heartthrob Jesse McCartney stopped by to visit patients and sign hats.
In other programs for Children's what calls their "frequent fliers," those who are hospitalized for 30 days at a time, get to set the menu and host a fancy dinner party at the hospital.
For Jayla Cooper, the wedding was an excuse to have a party and help others, according to the family's personal guardian angel, Shonda Schaeffer, executive director of the Grapevine Relief and Community Exchange Clinic, who has been raising funds to help the Coopers.
"One of the reasons she wanted to do the party is the number of people in this tight-knit community who have come out to help," Schaeffer told ABCNews.com. "And her dream was to be a bride -- so it kind of came up like a wedding."
"This little girl can teach us all a thing or two about living," Schaeffer said. "She's not afraid to die and has the most precious attitude."
Jayla has told her parents that she is "ready to go see Jesus and go to heaven." She says she'll miss her family but reassures her brother that "I'll come down from heaven one night and tickle your tummy."
For Jayla's mother, Lisa Cooper, agreeing to the last wish for a wedding was easy. "She's my baby," she said, before bursting into tears.
"She has come to terms with this better than any other child or human being in this world," said the 26-year-old. "It must be the Lord because she is stronger than I will ever be."
Jayla's mother does get angry when she sees so little attention paid to acute myelogenous leukemia (AML), a disease that in many other chronic acute forms has been brought into remission.
"This is my 9-year-old daughter," said Cooper, whose 22-year-old cousin died of AML. "They are children, babies, who don't get a chance to make it in life. They need to know that they are suffering, and we have to find a cure."
Learn more about the Leukemia and Lymphoma Society.
Contact the GRACE Clinic to make donations to the Cooper family.