Final answer:
Simon and Jan Pilkings are attending a Masquerade Ball for the royal visitor, an important event in Wole Soyinka's play that underscores themes of cultural identity and colonial tension.
Step-by-step explanation:
The event Simon and Jan Pilkings are attending for the royal visitor is a Masquerade Ball. This event is significant within the narrative of Wole Soyinka's play, where the characters are confronted with the complexities of cultural identity and colonialism. The ball is a site of cultural interaction and tension as the Pilkings couple, British colonial officers, unknowingly wear traditional Yoruba egungun costumes that are considered sacred, causing conflict with the local community.