@Henry257 your listing is entirely under your control. You can untick 'breakfast' under Amenities and then just state in your listing that breakfast is available on request (which you have already done) but at an extra charge. Then you can send a special offer to those guests who request breakfast (as long as they do this before they book). Alternatively, they can just pay cash for breakfast once they arrive.
@Henry257 I agree with the first suggestion. You could also just add the breakfast cost into your nightly price (if you charge for breakfast daily) and then you don't have to worry about it!
What about just sending them a welcome message with nice picture of a breakfast table and ask them would they like to include that? Then if they agree, make a reservation change.
I have a nice fireplace and I sell firewood to all who want it. I always send a small ad after the reservation and if they want it, make a price change request.