Book making is one of those activities that some children will choose right from the get-go and others will warm to over time. There are many ways you can make your own book templates (pop-ups are a favorite and this site will teach you how to make 3 different kinds) which are perfectly fine for the young authors in your program.
You can also buy pre made blank books that will provide a different kind of experience for children. There are several kinds available for purchase (if you shop around you can find some inexpensive types). The ones below are perfectly fine – however, filling a book this big is a HUGE challenge for young children, so I wouldn’t expect it. If you wanted to make a NUMBER book that children can work on over time, label each page with numbers and then allow children to work on them when they want until they are finished.