Kids interested need to submit an essay (250 word maximum) explaining why they want to spend May 13 with their moms at Chase Field to watch the D-backs and Giants.
Fifteen winners will receive up to four Legends Suite tickets and participate in a pregame meet-and-greet with McDonald.
The deadline for entering is Tuesday.
"I have a daughter, too, and I thought about how much my mom influenced me and had an impact on the goals that I had, what I did growing up and the type of person I am today," McDonald said. "There are a lot of moms out there who enjoy the game of baseball, who want to introduce their sons to baseball or their daughters to baseball and I want to bring them closer to the game as well."