I love rereading children's books. It's like re-meeting old friends. My choices:
Enid Blyton: Pretty much any, but especially Adventure series. First Choice: Castle of Adventure
Malcolm Saville: Lone Pine, Buckingham, Nettleford series. First Choice: Wings over Witchend
Monica Edwards: Punchbowl or Wrestling series. First Choice: Storm Ahead or The White Riders
Violet Needham: Not so keen on her non series. First choice: The House of the Paladin
Antonia Forest: I prefer her non-school ones. First Choice: Either her historical set The Players Boy/The Players and the Rebels or The Marlows and the Traitor
Geoffrey Trease: Great books. First Choice: Cue for Treason
Arthur Ransome: Prefer the Swallows and Amazon set. First Choice: Winter Holiday
Elinor Brent Dyer: Haven't got many outside the Chalet School. First Choice: The Princess of the Chalet School
Noel Streatfield: Love lots of hers. First Choice: Party Frock
Diane Wynne Jones: Great set again. Time of the Ghost is very creepy. I only read it as an adult though. First Choice: Power of Three
Pamela Brown: Don't like Maddie Alone but the others are great. Her non-series ones aren't as good either. First Choice: The Swish of the Curtain
Joan Aiken: Love the Dido set, but my favourite were the Saddle the Sea set. First Choice: Bridle the Wind
Elizabeth Gouge: I was absolutely over the moon to discover Island Magic on Kindle the other day. I have the other in that series. All of hers are wonderful. First Choice: Smokey House
CS Lewis: Obviously the Narnia set. First Choice: The Horse and His Boy
I could continue all day.