Hallo! I don't know of too many older translations of the play or novel, unfortunately, but one production in Germany was briefly mentioned in R.L. Green's fabulous Fifty Years of Peter Pan:
“Peter Pan does not seem to have been seen in France again until 1954, when the first verion to be acted in French, by Claud André Pujet, is promised by the Comédie Française with décor by Canzou, under the title Le Petit Enfant qui ne Voudrait pas Grandir, with a boy playing the name part.
This follows on the immensely successful production of the play in Germany which opened in May 1952 at Munich and reached Berlin during the Christmas season. It was translated by Erich Kastner* [sic], author of Emil and the Detectives, and to a certain extent adapted to suit German audiences, with Tinker Bell re-christened Kling Klang and accompanied by the sound of a Japanese carillon, Captain Hook interpreted as fat and greasy with no sign of the public school tradition about him, and Peter played for the first time on the professional stage by a young man instead of a girl.” (pgs. 147-148)
I wasn’t able to find much information on that early production, sadly. I was, though, intrigued to find an entry on Barrie (and Peter Pan) in Klassiker der Kinder- und Jugendliteratur: Ein Internationales Lexikon (1999; Band 1, pgs. 72-75). The relevant pages are available via Google Books (I’m guessing you’ve already checked out this book, but I’ll provide the link anyway):
https://books.google.com/books?id=SaAmDgAAQBAJ&pg=PA74&lpg=PA74&dq=1952+%22München%22+%22peter+pan%22&source=bl&ots=F1tbbrh_QG&sig=ACfU3U1uzYf3jOWIspLITsIy7PsP6JQC4g&hl=en&sa=X&ved=2ahUKEwiM1IOnyL3xAhXYl54KHWG7As4Q6AEwEHoECBIQAw#v=onepage&q=1952%20%22München%22%20%22peter%20pan%22&f=false
The list of translations written in the bibliography section of the entry is as follows (the first translation listed was from 1948…):
Übersetzungen: Peter Pan oder Das Märchen vom Jungen, der nicht groß werden wollte. K. Janecke/G. Blöcker. Berlin 1948. – Peter Pan. E. Kästner. Köln 1959 (in: E. Kästner: Gesammelte Schriften. 4.). – Peter Pan. H. Lemke. Düsseldorf 1955. – Peter Pan. E. Kästner. Zürich 1969 (in: E. Kästner: Gesammelte Schriften. 5.).* – Peter Pan und Wendy. E. Constantinescu. Bukarest 1972. – Peter Pan. E. Türk/G. Heppich. Wien/München/Zürich 1975. – Peter Pan. D. Lienerth. Bukarest 1978. – Peter Pan. U. v. Wiese. Düsseldorf 1980. – Peter Pan. dies. Würzburg 1987. – Peter Pan. B. Wilms. Hamburg 1988. – Peter Pan und Wendy. G. Bean. München 1990. – Peter Pan und Wenty. H. Nägele. Frankfurt 1990. – Peter Pan. P. Oliver. Erlangen 1992. – Peter Pan. A. Eisold-Viebig. Stuttgart 1992. – Peter Pan. dies. Würzburg 1996.
*(I’m curious on how the two Kästner translations differ, having been written ten years apart….Very intriguing!)
(As an aside, my personal German copy of Peter Pan (the novel; published 2009) was translated by Adelheid Dormagen. My German copy of Peter Pan in Scarlet (2006) was translated by Anne Brauner.)
Also of note (though I’m not sure if it’s relevant to your research) is Richard Ayres’ Peter Pan, No. 45 opera (2011-2014). The work was commissioned by the Oper Stuttgart and the Komische Oper Berlin, supported by the Ernst von Siemens Musikstiftung. The English libretto was written by Lavinia Greenlaw, the German translation of the libretto was by Adelheid and Jürgen Dormagen. I’ve only ever listened to the English version—I cannot find a recording of the German production (nor a preview of the German score/libretto). The opera wasn’t targeted toward any particular age group, but I recall seeing reviews on it that noted the complex harmonic language might have made it a little challenging for young people to comprehend.
Here's a link to the score with information on performances, etc.: https://en.schott-music.com/shop/peter-pan-no-45-no262547.html
What an absolutely fascinating subject for your thesis! Alles Gute. (As you posted in 2015, I'm supposing you've since finished your research and writing. If not, however, I wish you luck!)