I first read this book myself when I was only 13 years old, quickly followed by another of Richardson's books, Lords of the Earth (which has even MORE horrific stories of martyrdom). I will never forget the day I read the last page of the second book, because as I finished the final page and closed the book, I distinctly felt God's call upon my life for ministry for the very first time. God used these books to create a heart for the Lost in me that has never gone away. These books were life changing for me.
I would encourage you to give the book a chance if you want to get ALL of what I believe Sonlight hopes that you get out of this core. Perhaps a compromise could be to use it as a read-aloud, but to omit it altogether would leave out what I think is a vital element in the Core.
Here's why...
While Peace Child can certainly be skipped and the academics of the core won't be affected, I want to suggest that the heart of what SL hopes you and your family will learn from this core will be affected.
There is a spiritual aspect of this book that is difficult to find elsewhere...the amazing story of how God left a "redemptive analogy" (see another of Don Richardson's books, Eternity in Their Hearts for more about what this is) within a culture which had departed so far from that Truth that remained deep within their traditions--and how the re-discovery and full understanding of that "redemptive analogy" transformed a people is unforgetable! There is an unmeasurable aspect of Sonlight that desires to develop a heart for the world in our families and an understanding of different world views and how they can be reached with the life changing message of the Gospel. Peace Child is difficult to be matched in its ability to show us how many tribal peoples in our world still think and view the world...and yet they CAN be reached and TRANSFORMED.
From an academic perspective, one reason I believe SL includes it is to present 20th century American tribals while you're studying about the ancient native peoples of North and South America. The lives of the people in Peace Child reflect that of many of the tribal peoples of the Americas encountered by the Spanish conquerors (though one might say they pale in comparison to the Aztecs, for example!). By observing a 20th Century culture that was untouched by "modern living" it provides us a unique opportunity to understand what it was the explorers of the 15th century and later encountered. It's like having a window to take us back in time five centuries!
So can you get plenty out of this Core without Peace Child? Certainly...so in that respect, I suppose its not "necessary". But there is an impact that reading this book will have that is difficult to replace...so in that sense, I'd say it is a necessary element. While not a "spine" or "pivotal" element of the course, it was not thrown in just to fill up space nor to simply provide an interesting missionary story. It does fit into the Core from a historical perspective and as we see the difference in the approach of Don Richardson and others in presenting the Gospel to these people as compared to the approach of the Spanish and others throughout the 15th through the 19th centuries, it can also break your heart to see how much MORE could have been accomplished in reaching people like the Aztecs, the Mayans, the Incas, and the "Indians" of North America to Christ if only similar methods had been utilized. What an opportunity was lost!!! It should break our hearts, and by reading what IS possible with such a people in Peace Child, that heartbreak is I think a very crucial part of the learning Sonlight wishes us to gain from this core.