my niblings are 5 and 6 respectively. they like to read and be read to and I would like to get some books to help foster their enjoyment of reading as they grow up - so ideally stuff that’s not too challenging but still good for fostering young imaginations. obviously sneaky subversive themes are welcome - the sneakier the better, I kinda suspect their dad leans chud.
Dr. Seuss books are very accessible at that age. I particularly like Oh The Places You’ll Go. Richard Scarry’s Busytown is another fun series. Then there are the oldschool Magic School Bus books. Another all time favorite is Dinotopia just for the imaginative worldbuilding of a utopian society. As they grow older you can’t go wrong with Roald Dahl.
I’m also going to second A Wrinkle in Time.