Invariably some of the most joyful performers in the season, the members of the Boston Children's Chorus return to the Gardner Museum for a fascinating and open-hearted program. These terrific young musicians have chosen to address one of the most pressing questions of the day: All of us, and especially our youth, are discovering who we are, how we identify, who we want to be: what would we see if we looked past the surface and embraced others for who they are and for how they see themselves?