Here is a great tool to get your younger children to write a book report. I use this template to get my 7-year old to write a summary after he reads a book. It is very simple.
The child simply fills in the following information on the one-paged sheet and gets to rate the book in his or her opinion by number of stars:
-Location of where story takes place
-Best part of the book & why
-And would they recommend it to a friend.
This is a great tool to use because it gives the reader some sort of control, as they get to rate the book and choose whether they would recommend the book or not. It allows the child some autonomy in within a structured format.
I highly recommend this template!