Is more memory worth more then a newer model if they are similar price?
I think it’s usually the other way around, as memory could be managed (e.g. by storing things in the cloud), but hardware specs and iOS updates can’t. I’d take the newer model.
Asking rhetorically: What’s your use case for the iPad, and is this your primary device? Also, how big is the price difference and how significant is that amount of money to you?
If you’re getting something for your kids, I’d say get the cheapest one (iPad 9th gen WiFi 64gb), and a good durable case.