Answer: Georges Hautecourt
When we first see Adelaide entering her house with her parcel, she stops and says "Oh, and Edgar, I'm expecting my attorney, Georges Hautecourt. You remember him, of course?" Edgar replies with a gleeful "Of course, Madame . . . how could anyone forget him?" In the opening credits, though, he is merely listed as 'lawyer.'
The other three names are of other Disney characters: Roger Radcliffe is Pongo's owner from "101 Dalmatians", Padraic Ratigan (yes, the books say his first name) is the main villain from "The Great Mouse Detective", and Preston Whitmore is the old flexible man, and friend of Milo Thatch, from "Atlantis, the Lost Empire".