The son of former Dublin goalkeeper John O'Leary is to walk out on to the Croke Park pitch today.
Tom will present the referee with the match ball as Dublin take on Galway in the All-Ireland semi-final at 5pm.
The seven-year-old was born with a heart condition called 'tetralogy of fallot' and he has a rare chromosomal disorder.
The money raised will go to the Jack and Jill Children's Foundation.
His dad, legendary Dublin keeper John O'Leary, who is on the board of the charity, describes what will happen:
"He's going to present the ball to the referee," he said.
"It's going to happen on the sideline just before the players are presented."