I've been re-reading the Swallows and Amazons series and have been very struck by how unsexist Arthur Ransome was, even by modern standards, never mind the standards of the 1930s and 1940s when he was writing. Lots of his female characters are what might now be called gender nonconforming. Fortunately at the time whether wearing shorts or skirts nobody seems to have questioned whether what they were doing was ladylike or seemly for girls (except the Great Aunt, who is quite obviously stuck in the past and WRONG).
Nancy Blackett is the undisputed leader of the Swallows and Amazons. She and John are firm friends and have great respect for each other's different skills and traits.
When the action moves to Norfolk, the twins Port and Starboard are brilliant sailors and equals to their friend and neighbour Tom Dudgeon. In Secret Water, Daisy is a Nancy equivalent.
Mrs Barrable, the Admiral, is a painter who used to be a schoolteacher. There are lots of strong adult women in the stories. Great-Aunt Maria is a dragon but we get some insight into why and she is beholden to no man.
Missee Lee - need I say more, to anyone who's read it!
Susan Walker - over and over again AR points out that the Swallows and Amazons would have been totally unable to do what they do without her hard work keeping them fed and safe. The adults trust her judgement implicitly. Everybody defers to Susan, even Nancy. No question of pooh poohing women's work as trivial.
Cooking - as and when necessary, male characters step up to the mark and cook for themselves and often for others too. They wash up , go shopping, tidy up. It's never written off as women's work or demeaning.
Dorothea Callum - arguably the pivotal character in The Big Six. Her powers of imagination and organising facts are key to the resolution of the travails of the Death and Glories.
Titty - I think the most interesting character of the whole lot. Incredibly well realised.
Mrs Blackett and Mrs Walker are far from being bland Mummy figures in the background. Mrs Dudgeon is a SAHM but has the confidence to disagree with her husband.
So I think you could do a lot worse than introduce your young readers to the Swallows and Amazons series.