Ideas for books for my DDs with strong female characters?

[BigFatLegsInWoolyTIghts]

DDs are 8 and 4. I got a great one for DD who is 4 "The Night Pirates" in which a little boy is woken up by a shipful of female child pirates....they take him away with them to take treasure from some bad adult pirates and then return him and sneak away.

It's lovely to see my DD get all excited...she's very physical, very into super hero behaviour and really believes in her own strengths...so I want to help her to celebrate that.

DD 8 is very vocal on equality and she's also an extremely fluent reader. She prefers books for older children but I don't want her to read anything too scary or too mature.

I'd love some suggestons if anyone has any?

For you four-year old:

Keep Climbing Girls

The Pirate Girl - Cordelia Funk

I'm not so good on recommendations for younger children, but for DD1:

Anne of Green Gables
Flambards - the first book is not too mature, I think I read it at about that age. Has a very physically active lead character.
Little Women
Little House books
The Anastasia Krupnik series by Lois Lowry
A Traveller in Time - Alison Uttley

thanks for the help. I have a huge Pratchett collection which she has read avidly. will take a look at Margaret Atwood and Jasper Fforde.