Let's expand a bit (while sticking to my earlier idea of 'Victoria' (probably called 'Vicky' in daily life)).
Names already in the (wider) family:
Beatrice: Beatrice Elizabeth Mary
Edo: Edoardo Alessandro
Wolfie: Christopher Woolf
Grandparents (with their parents)
Andrew: Andrew Albert Christian Edward (Philip & Elizabeth Alexandra Mary)
Sarah: Sarah Margaret (Ronald & Susan)
Alex: Alessandro (Gian Paolo & Gigliola)
Nikki: Nicola Diana (Susan Arnot & Robert David)
Siblings:
Eugenie: Eugenie Victoria Helena (with child: August Philip Hawke)
Natalia: Natalia Alice
Alby: Albemarle Christopher
My guesses (in doubt about 2 or 3 names)
Daughter: Victoria Alexandra ('Vicky')
--> Alexandra is both in reference to the queen and Edo's father (and himself)
Son: Fergus Albert
--> Had a really hard time coming up with an acceptable first name for a boy until I found
this list of true upper class names: and Fergus stood out in connection to the name 'Ferguson' (not very likely but it would be a bold choice).
--> Albert in reference to Beatrice's great-grandfather AND queen Victoria's husband (and grandfather Andrew ALBERT ...)
EDIT: Name of Albemarle into Alby (thanks to TM).