Here is Mikko Kiviharju's comments about the Finnish version of Don Rosa's Duck Family Tree, dated from November 23rd 1999.

The comparing with the US version of the names goes as follows: I have listed the US name followed by the Finnish name and after that the exact translation of the Finnish name, unless it is the same. See comments below.

The Clan McDuck = MacAnkan Klaani

Matilda McDuck = Matilda MacAnkka (-''-)
Scrooge McDuck = Roope Ankka (u)
Hortense McDuck = Hortensia MacAnkka (-''-)
Downy O'Drake = Lauha MacAnkka (Temperate McDuck)
Fergus McDuck = Fergus MacAnkka (-''-)
Jake McDuck = Jake MacAnkka (-''-)
Angus "Pothole" McDuck = Angus "Hiidenkirnu" MacAnkka (-''-)
Quagmire McDuck = Lordi Ohrapää MacAnkka (*)
"Dirty" Dingus McDuck = Kalle Ankanpää (Carl Duck-head **)
Molly Mollard = Molli MacAnkka (-''-)
Sir Roast McDuck = Sir Mahakas MacAnkka (Sir Big-belly McDuck)
Sir Swamphole McDuck = Joonas MacAnkka (Jonas McDuck)
Captain Hugh "Seafoam" McDuck = Julius MacAnkka (Julius McDuck)
Malcolm McDuck = Malcolm MacAnkka (-''-)
Sir Quackly McDuck = Rikhard Ankanmieli (Richard The Duck-Minded)
Sir Stuft McDuck = Sir Rahakas MacAnkka (Sir Wealthy McDuck)
Sir Eider McDuck = Ritari Kananjalka (The Chicken Foot Knight)

* "Ohra" is a crop, looks like rye, but it is used for beer-brewing. "Pää" is "head".
** Interesting, but the translation is identical with the translation of the Coot Kin. To be exact, this should be Carl Coot.

The Duck Family = Ankan Suku

Huey Duck = Tupu Ankka (u)
Dewie Duck = Hupu Ankka (u)
Louie Duck = Lupu Ankka (u)
? Duck = ? Ankka (DH&L:s father)
Della Duck = Della Ankka (-''-)
Donald Duck = Aku Ankka (u)
Gladstone Gander = Hannu Hanhi (u)
Fethry Duck = Touho Ankka ("touhottaa" is a verb meaning "to fuss around")
Abner "Whitewater" Duck = Sisuvius Ankka (from Finnish "sisu" = guts)
Quackmore Duck = Aaron Ankkav (u)
Goostave Gander = Hjalmar Hanhi (u, but the surname means Goose, not Duck)
Daphne Duck = Dora Ankka (u)
Lulubelle Loon = Aino Ankka (Aino was the name of a girl, who Väinämöinen sought to be his bride, and who drowned herself because of it, in Kalevala. Also considered in appearance the ideal Finnish woman.)
Eider Duck = Unto Ankka (u)
Humperdink Duck = Hepsu Ankka (u)
Pintail Duck = Puosu Ankka (Puosu is some kind of position or a job in a schooner)

The Coot Kin = Ankanpään suku (The Duckhead Family)

Gus Goose = Hansu Hanhi (u)
Fanny Coot = Hanna Hanhi (u)
Luke Goose = Martti Hanhi (u)
Cuthbert Coot = Serkku Kiljuhanhi (Cousin "Lesser White-fronted Goose" (*))
Elvira "Grandma Duck" Coot = Kaino-Vieno "Mummo" Ankka (Shy-Delicate "Grandma" Duck (**))
Casey Coot = Konrad Ankanpää (u)
Gretchen Grebe = Gerda Hanhi (Gerda Goose)
Gertrude Gadwall (?) = Olga Ankanpää (Olga is an old, Russian name. Sometimes used in derogatory tone in WW2 to describe young Russian maidens. Notice the same surname as with Coot)
Clinton Coot = Kornelius Ankanpää (Cornelius Duckhead !)
Cornelius Coot = Julle Ankanpää (Julius Duckhead)

* A dwarf goose.
** Kaino is an actual name also, used for both men and women alike. I'm not sure about Vieno if that's an official name.

Close Family = Melkein sukulaisia (Almost relatives)

Daisy Duck = Iines Ankka (u)
April Duck = Leenu Ankka (u)
May Duck = Liinu Ankka (u)
June Duck = Tiinu Ankka (u)
Gyro Gearloose = Pelle Peloton (Clown the Fearless (*))

* Pelle is an actual name also

Notes:

u = The Finnish name given is so normal that I am unfamiliar with its etymology, and thus I am unable to give any proper translation for it.

The version I compared the names with was "Don Rosa's Duck Family Tree - The 'original' version" found at:
http://members.xoom.com/sigvaldg/donrosa/tree_us.html

Compared to the Finnish family tree, Quagmire McDuck and Sir Swamphole McDuck have switched places, as have Sir Eider and Stuft McDuck. Otherwise the places are identical.