About your creation myth, I've heard this in several variations both in Nigeria and the diaspora, but never has Orunmila been involved, always Orisa Nla. As a bababalwo, I understand that Orunmila is Eleri Ipin (witness to creation), witness, but not the actual creator himself. I'm fair positive you might want to modify this story to reflect that. Can I ask where you heard this version?
In answer to that question, I am unable to cite a source. I wrote the story as remembered from numerous tellings and retellings (with slight variations) from many years ago. It is quite possible that I have the characters in the story switched up. He also suggested a book on the subject:
From a scholarly standpoint, a very good english version is in the book called "Olodumare: god in Yoruba belief" by Prof. E. Bolaji Idowu the former head of the Department of Religious Studies, University of Ibadan, Nigeria AND fomer head of the Methodist Mission in Nigeria. Though a christian, he was very interested in traditional thought/practices and did a very good job in the book of presenting the stories without a christian bias.I will have to update the story as soon as possible and hope I have not mis-educated too many people in the interim. If you know other versions of the Yoruba creation myth, I would love to hear them - you can post in the comments here or send me a note.