Dear Mary: how do I stop my book club banging on about their grandchildren?

Q. At the Ludlow Piano Festival, during a Tyler Hay concert, my husband and I spotted a fascinating-looking couple who were fellow members of the audience. We longed to know who they were and are kicking ourselves that we never found out the identity of this charismatic pair. During the interval we could have approached them but didn’t want to seem pushy or pervy by just introducing ourselves.