The Adventures of Priscilla, Queen of the Desert
(1994)

Tick (Hugo Weaving) faints on stage after seeing his son at the performance where he, Adam (Guy Pearce), and Bernadette (Terence Stamp) have just done their big drag revue. But it turns out Benji is not only OK with his estranged father's career (and sexual preference), but he's proud of him and wants him to be happy. Tick agrees to take Benji for the summer so they can spend some time together.

The boys fulfill Adam's lifelong dream of climbing Kings Canyon in full drag.

After their stint at Tick's wife's resort is over, Bernadette decides not to return to Sydney with them--opting to stay with Bob, with whom he has grown very close.

Before leaving the resort Benji had made Tick promise to let him see him do his famous Abba performance, so just before the credits roll we see Tick and Adam, back in Sydney, performing to "Mamma Mia" ... with Benji watching from backstage.

Thanks Greg B!