Breakfast Plans - How do I custom modify them?

Good afternoon, 

I hope someone will be able to assist me with this.

At my property, I offer breakfast (continental and a cooked traditional English) to my guests. The continental is included in the room rate. 

Guests that stay 1 night, pay for a cooked breakfast. 

Guests that stay for multiple nights get a cooked breakfast included in their room rate

Children eat free regardless

I see zero function in the Facilities & Rates for me to set the above. To clarify for my guests, I have a Welcome template which explains the above but of course, guests will have already paid for breakfasts when they make their bookings through booking.com. 

I then have to contact Booking.com and request a modification to a guest's booking. I have emails notifying me that I can modify a guest's booking via the Extranet, by going into Reservations, selecting guest name, then choosing the "Change Reservation Dates & Prices". I have notified Booking.com this option is not available to me as the pricing part is not present. 

After having requested another booking modification, today I received another email containing the following message: "We highly recommend you to change the price/meal plan settings if breakfast will be included in price for multiple night bookings."

I have looked on the Extranet and I do not see at all where I can customise modifications to reflect guests only pay for breakfast if they stay one night, otherwise it is free & children eat free any way. 

I apologise for the long post but hope I have been clear with the issue I am having. 

Kind regards, 

Jay