The Dropkick Murphys will perform during Opening Day festivities at Fenway Park on Friday. The band is also playing a sold-out, acoustic benefit show for the families of Lieutenant Edward J. Walsh Jr. and firefighter Michael R. Kennedy at frontman Ken Casey’s bar McGreevy’s on Sunday night.Mark Shanahan can be reached at email@example.com. Follow him on Twitter @MarkAShanahan. Meredith Goldstein can be reached at firstname.lastname@example.org. Follow her on Twitter @MeredithGoldste.