The 300 win mag is definately not too much gun. And if this happens to be what you feel is your best shooting gun, (that is the gun that you should take) Your 270 and 30-06 will kill them also. But it is your confidence in your 300 win mag that should lead you to bringing this gun. I have seen quite a few caribou taken with .308's...so your 300 win mag is plenty gun for your hunt.
GOOD LUCK HUNTING...I HOPE YOU KNOCK EM DEAD