Your wife may guide your lips over his cock, but only you can open them and take that cock. You won’t even realize that you are sucking his cock immediately. Will be a few head bobs in when you realize this and by then you won’t be able to stop yourself. In that moment you’ll be wondering how much more of his cock you can take and find yourself trying to find out.
The wife will sit back and give you instructions. She will encourage you. And when he cums, she’s not letting you off his shaft until you have swallowed every drop. (Though it’s not like you’re going to try to spit it out.)
In that moment, your ass will be quivering in anticipation of what is next.