ok maybe I'm not reading this right but...
You have a squad that is charging/being charged...when you are talking about contributors are you talking from the same squad or from another squad that is within two inches...
If you are refering to models in the same squad then everything in that squad within two inches of the point of contact (where the two opposing squads make base to base contact after the assault move) is considered charging and gets their full attacks as well as the +1 charge bonus...the 'back rank' rule applies after initial HtH and counts for those squad models that cannot make a wrap move and are stuck in the melee in the rear rank...where they only get 1 attack at their base stat line...also known as lending attacks...
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I am Wolfpack, my fangs are long, my hair grey with age...I am The Great Wolf...I fight with bolter and Axe, my armies vast, my word final. A true son of Russ, my honor above all, I hunt the heretic, the xenos, and the witch and slay them where they stand! My sons hunt our enemies,
slay them where they falter and bring their pelts to Fenris