In my house manual, I say that door codes will be messaged to guests on check-in day. Then after the room is ready, I go to the message center use the saved message that is my house manual and change the verbiage.
For example, the house manual that they can see after the book says "The entry code to the door will be messaged to guests on check-in day using the AirBnB messaging system." but in my message that I change it to "The entry code to the door is 1234" and send it.
Since my listing does not include parking I put the name of the park contractor, location of the parking garage and approximate cost of the on-site parking in my house manual. I also include a picture of the rate sign edited with text giving the date of the photo and the disclaimer 'subject to change'
I have had no complaints. I also put the codes in the message twice once at the very top as a summary and then once in the body of the house manual where I explain how to actually use the combination lock.