Michael Rosen is a Marxist. We're all Going on a Bear Hunt is a classic. I'm sure he published a collection called Socialist Tales, too. Could be worth a look. He narrates a lot of his stories and poems on his YouTube channel. He also wrote three books about getting kids to write. There's some good stuff in them, although it's focused on what teachers can do with young pupils. And a lot of the chapters are things rewritten from his blog. (His older blogspot blog, mind; I'm unsure if he writes on his 'official' blog so much.)

I enjoyed reading the Grufalo to my little cousins when they were that age. Julia Donaldson did one about a witch, too. Something about a cool broomstick. I don't remember the title, sorry. Superworm is great, though. There's also a Julia Donaldson Treasury of Songs, which is a good accompaniment to her books. There's a playlist of the songs on Spotify.

When they get a bit older (early teens, maybe), Mark Haddon, Curious Incident of the Dog in the Nighttime is good. It's about an autistic boy so I think it'll be a good one to subtly teach about neurodiversity. But I wouldn't see it as only that as it's a good story, too.

Isadora Moon is good. The one about going to school is the 'first' one but the author says to read them in any order. If you are introducing Spanish as LaGG_3 mentioned, this is a good one for it. I read the translation for myself and it's simple language about everyday things. Probably too complex if they don't know any Spanish. But not a bad place to start if they're marginally bilingual. Originals are in English, I think.

I'm not entirely sure what's age appropriate but the author who wrote the Very Hungry Caterpillar did a few books about: a polar bear, a brown bear, 'head to toe'. They're quite repetitive. I like them as there are bilingual editions. But be careful as the prices fluctuate. Don't get mugged! Wait till the prices come down if you want them. Maybe after Christmas would be a better time to get them. (The English editions tend to be a better price year-round.)