You said deer and 100gr bullets at the same time. Pretty much rules out the 308 and the 260, the 7-08 and the 7mmWaters. You must be a reloader? My first two choices would be the 257 Roberts and the 250 Savage. The 243 will certainty work but runs out of bullets at 100grs. The 25 cals are just getting into hunting bullets at 100grs. The 25-06 is a fine cartridge but depending on the kids, may be a bit to violent. What a small kid may thrive on, a big kid might find objectional. The size and age of the kid is not necessarily a good indicator of what recoil they can handle. And it's not just recoil, it's also preceived recoil. That's why I said the 25-06 may be to violent. Of course if you reload, 7mm Waters?, then any on your list could be used. Think I'd go for a min 130gr in 7mm's and a min 150gr in 308. All can be loaded down.