thank you for this important and interesting topic!
In my experience toys more are relatively undefined and more they develop imagination, that is a seed for creativity. The best are toys made by parents.
Tinkering is also a important topic . Children should be left free to experiment objects and words, so two books I like and I used with my children are:
- Toymaking with children by Freya Jaffke
- The grammar of fantasia by Gianni Rodari