Adam Davis of far northwest suburban Huntley, a sixth grader, has been training for the 13.1-mile run. He also volunteered to push a friend, Justin Moy, who uses a sport wheelchair.
Moy was scheduled to fly in from Massachusetts Friday night.
Davis says he wants his friend to know what it feels like to run.
" I'm a little nervous," the 11-year-old said. "My mom says I can do it, so then I believe I can do it."
The two boys have not been able to train together, but Davis has logged hundreds of miles and even tried to run with his 4-year-old sister in a stroller -- but she cried when they got to the end of the driveway.