Diamond benefits are for the member only.
Thus for the member's own occupied room.
Diamond welcome amenity: breakfast
As per T&C
https://www.ihg.com/content/us/en/cu...er-tc/2nd-page
Welcome Amenity: The Welcome Amenity for Platinum Elite and Diamond Elite Members varies by brand and region. In Greater China, Silver Elite and Gold Elite Members are also offered a choice of Welcome Amenity.
- The choice of amenity is only offered on Qualified Stays and is non-transferrable
- Diamond Elite Members’ Welcome Amenity choice also includes Free Breakfast at full-service and select limited-service brands (REGENT, InterContinental, Vignette, Hualuxe, Hotel Indigo, voco, Crowne Plaza, Even, Holiday Inn, Kimpton, and select Garner Hotels)
- Available for Member and one guest registered to the same room for each night of stay
- Includes one main menu item with unlimited non-alcoholic beverages or full buffet with unlimited non-alcoholic beverages per person
- Select Breakfast menu items may be excluded (such as specialty/local-themed items)
- Alcoholic beverages and certain specialty drinks excluded
- Not available for In-Room dining or at specialty restaurants
- Not offered at InterContinental Residence Suites Dubai Festival City, InterContinental Doha Residences or InterContinental Alliance Resorts Macau.
That's the official way by the book.
Your room's occupancy with you +1 in it , will enjoy the diamond welcome amenity: breakfast.
Your extra room booked that is occupied by your son would not get auto-granted free breakfast.
So it's good that you booked for him a breakfast inclusive rate.
In my situation as diamond, i occupy my room with S/O and get complimentary breakfast
My kids share together an extra room and although it is booked under my name, they do not get complimentary breakfast.
Hence i use the milestone nights awards: F&B vouchers to offset their breakfasts or like you do, book a breakfast inclusive rate for them, or write to the hotel how much breakfast add on will be if they are booked in an award room.
Hope this clears it up.