I’m certain that your children have a lot of different toys around the house. Try incorporating those toys during their reading time to make the stories come to life and to further develop their creativity.
My two sons loved to read about dinosaurs, and we must have had every type of dinosaur toy in our home. We also had lots of dinosaur books - fiction and nonfiction. When my late husband and I read a dinosaur book with them, we often connected the dinosaur in the book to a dinosaur toy that they had. Many times, during their play time, we would see them lining up their dinosaurs to go on an adventure or to get ready for battle. They would make up stories and the dinosaurs were their characters in the stories.
The same can be done with other toys such as dolls. A doll can become a character in a book and then later, your child can use the doll in other stories that she creates. There is no limit to what can be done and how much fun can be had.