Lou Merloni, former Red Sox player and cohost of WEEI-FM’s (93.7) “Mut and Merloni” midday show, cochairs this year’s Room to Grow gala Dec. 7 with his wife, Steffanie. Twenty years ago, Steffanie was an unmarried single mother living on Cape Cod and facing an uncertain future. Today the Merlonis, who live in Marshfield with their 3-year old son, Mason, are loyal supporters of the nonprofit organization, which serves 350 needy families in the Boston area by providing clothing, baby equipment, toys, books, and other services.