During research for vintage, (Christian) children’s books, I also found these (Sorry, most books are with bib overalls, very soon on my other blog).
-Elli Kühne: Schlüpp und die Lederhosen
-Elli Kühne: Schlüpp und die Lederhosen – Eine Nummer größer
-Pic above Knabenbuch 1900s (funny cover)
Please note, that I don’t know these books. So it’s possible and likely that there are no mentionings (or illustrations) of Lederhosen and sailor suits (as they were normal clothes these days). And the Schlüpp kids are maybe very young (3 boys depictured on book 1). Therefor many books are about spanking.
Currently I’m reading Enid Blyton books. There are some very good TV adventure series with boys and girls in bib overalls and shorts. More books