Donnie Wahlberg (left) helped construct a playground for the Waltham Boys & Girls Club. (Bill Brett for The Boston Globe Hours before the game at the Garden, Celtics fan Donnie Wahlberg joined a pack of New England Patriots, including No. 12 Tom Brady and owner Robert Kraft, at the Waltham Boys & Girls Club for the building of a colorful new playground — while a throng of fans snapped picture after picture. A great time was had by all, including Wahlberg, who costars on the CBS cop drama “Blue Bloods’’ with Bridget Moynahan, who, rather famously, is Brady’s ex. “. . . Everybody thinks that’s a big deal,’’ Wahlberg said, “but it’s not. Tom’s, like, the greatest and I’m a huge fan, and Bridget is, too.’’ Of course, Donnie isn’t above talking trash — when appropriate. “[If] the Celtics stay healthy, no one is going to be talking about [the Heat] in May or June,’’ he said. “. . . It’s like gossip page stuff now. That’s what the Heat are right now. They’re like gossip fodder.’’ Do...