As a therapist I have used a few of the mainstream DBT books that help clients individually and in a group setting and while they are good, I would like for you consider the following workbook as a great addition for your DBT toolbox.
Carol Lozier is a wonderful DBT writer and social worker who has been doing this for 30+ years and has written other books on DBT and helping those to understand the skills.
I was gifted this book during the COVID-19 Pandemic and while writing my own workbook. This workbook is so wonderful for children who are in an age group that I am not trained in ( under 14 ) and she does such a great job with her examples on mindfulness and how she describes these abstract ideas/concepts to a younger population. She has some wonderful activities for the parent/caregiver or therapist to use with the client. I have not seen a workbook for this age range that truly tackles all of the DBT skills.
If you would like to know more about Carol Lozier and her other books you can find her at www.carollozierlcsw.com. You can also purchase her book on her website or from amazon.