I know you want something in the 6.5 caliber range. The 6.5 Grendel in something like a mini action would be a great combo. If it was me though, and I compare the 6.5 Grendel to the 6 arc. The arc is the clear winner if I’m starting from scratch on a new to me caliber/rifle. I understand you already have .243 and are not that big on 6mm for hunting. But if you could put your kids behind the arc and see the benefits of that cartridge and also do some research and see what some of the heavy for caliber bullets in 6mm do to animals, you might change your mind. I have gone through training with all 3 of my daughters and im telling you the flinch is real. I started my oldest daughter on a 6.5 creedmoor and that was a big mistake. If I had it to do all over again they would be outfitted with 6 arcs and either the 103eldx or the 108 eldm. From a terminal ballistics standpoint, i would prefer a long 6mm bullet like the 103eldx/108eldm to the short/light for caliber 120eldm/123sst 6.5 bullet for hunting deer and elk. But if you decide to keep it between the 7mm-08 vs 6.5 creedmoor. The creedmoor is the better choice.