Is it a good practise to use a character’s face inset during a conversation style academic text book through out the book used by kids?

To give a context - We are designing an e-book, teaching basics of computer science for kids aged 6-10. The narration style is similar to a chat conversation involving 2 kids (learner) and 1 mouse (mascot-mentor). This style is used across the book which the kid will be using for one whole year. So on the e-book there is a dilemma whether to use the character faces through out the book or only on the initial page of every chapter and occasionally use the whole body of the character in between the chapter.

Argument 1: - To use character faces throughout the book

Because - Its for lower grade kids and they will be relating to the character what it is actually conveying - They might get confused which character is speaking - It will look good to have those cute character faces in the book

Argument 2: - To use character faces only at the beginning of each chapter and later use only unique initials and colors to represent specific character

Because - Having face value is good but to use it through out the page/book will distract the user from the primary goal of learning a new concept - When we use a character in a book we want the user to remember the character not only while reading the book but also while away. In order to achieve that -- we introduce the character at the beginning of each book with animation (not just the face but the whole character body) -- we also show the face inset at the beginning of each chapter with its respective name, initial and color -- finally we allocate each character with a color which is used for its dialogue call out - And in most cases it doesn't really matter who is speaking the dialogue because what really matters is what they are speaking (the concept)