The shift to an indoor venue Saturday couldn’t diminish the annual March for Babies’ celebration of healthy babies and the March of Dimes’ 75th anniversary.The walk, held in Otwell Middle School’s gym, was bittersweet for Jessica and Matthew Shuman. In March 2011, the couple lost their twins, Drake and Alice, who were born months ahead of schedule.Their daughter, born at 22 weeks and son, born at 23 weeks, were too small to survive, Jessica Shuman explained to a crowd of walk participants. “We walk for our twins,” said Jessica Shuman to the crowd of about 300 participants.