Im a spanish speaker I do not know how to properly call this kind of "pages".
The pages and the end of a children books that are meant to play or have figures for children to cut.
In spanish we call them "hojas desglosables"
An Activity page is often used to describe pages in a children's book that are more interactive than narrative. Here is a great example of a book, Fabulous Fables, with an activity page section at the end.
The term activity book, would be a book containing mostly activity pages.