Summary:
The fairy Iolanthe has been banished from fairyland for 25 years, because she married a mortal; an act forbidden by fairy law. Her comrades convince the Fairy Queen to lift her punishment. Much rejoicing ensues.
Iolanthe has a son, Strephon, who is an Arcadian shepherd. He wants to marry Phyllis, a Ward of Chancery. Unfortunately, all the members of the House of Peers also want to marry Phyllis. They conspire to take her away from him by showing Phyllis an embrace between mother and son. When Phyllis sees her beloved hugging someone who appears to be a young woman (immortal fairies all appear young), she assumes the worst and sets off a climactic (and musically complex) confrontation between the peers and the fairies.
The second act involves reconciliation between the lovers, and includes much commentary on politics which is still surprisingly relevant today.
(Edited from source material on Wikipedia)
https://en.wikipedia.org/wiki/Iolanthe
Iolanthe is suitable for all ages.