For book ideas, the Fairy Math Mother is a great resource. [0]

I highly recommend getting a set of Tiny Polka Dot cards. [1] It comes with lots of ideas for games but it's also open-ended — we've had a lot of fun coming up with our own games to play with the cards. It's extra fun when you mix them in with toys; e.g. build a race track out of blocks and then draw cards to move your characters along the track to see who can get to the end first.

There's a BBC show called Numberblocks that my 5yo loves. I made an exception to my no-cartoons policy for this one and I'm really glad I did. It presents a whole slew of mathematical concepts in a very visual way. The full episodes are available on Youtube if you know where to look — beware that there are a ton of compilation videos that just show snippets which is frustrating. But if you go to the "Red Level" "Orange Level" etc. playlists, you'll get the full episodes. [2] We also got a set of buildable Numberblocks characters and he enjoys retelling the episodes with them.

There's a great blog called Talking Math with Your Kids that's full of little transcripts of conversations the blogger has had with his kids. (You can also pay a few bucks to get the ebook which is a little more organized.) The blog has good tips for how to ask questions and follow-up questions that give kids a chance to explore and express their thinking on different topics, as well as ideas for situations where you might initiate a mathematical conversation. [3] This blog sparked a #tmwyk hashtag on Twitter which I enjoy, since it's just parents posting their own little snippets of conversation. [4]

I haven't found a lot of resources for little kids that focus on computing concepts, so I just make up my own stories, some of which I've documented on my blog like "Pickle and the Boolean Logic Baby Gate" [5] and "Pickle and the Closet of Functions" [6]

I also recommend having some manipulatives on hand that can help with figuring out the answer to questions that come up. My son is very curious about math and will often ask us questions (the other day it was "what's four to the four?"). I can show him some things with paper and pencil, but he hasn't done much multiplication yet so after we figured out that 4 x 4 x 4 x 4 = 16 x 16, we got out the base ten set [7] to figure out how many you have when you have sixteen 16s. He carefully counted out 16 copies of a 10 rod plus 6 ones and then I showed him how we can exchange 10 unit cubes for a 10 rod, and 10 ten rods for a hundred square and he was able to figure out the answer from there.

We haven't done as much with science, but we like to go to the library and I'll find books in the non-fiction kids section that are relevant to his interests. E.g. he started asking a bunch of questions about sound and how it travels, so I found a library book that had some simple experiments we could do at home together.

[0] https://fairymathmother.com/
[1] https://mathforlove.com/games/tiny-polka-dot/
[2] https://www.youtube.com/watch?v=fC_0LqcEsu8&list=PL9swKX1Pvi...
[3] https://talkingmathwithkids.com/_blog/
[4] https://twitter.com/search?q=%23tmwyk&src=typed_query
[5] https://bancosparenting.wordpress.com/2021/05/08/pickle-and-...
[6] https://bancosparenting.wordpress.com/2022/03/13/pickle-and-...
[7] https://www.amazon.com/hand2mind-Complete-Manipulatives-Kind...