Unfortunately you should do what your guide wants on the hunt. That is why its best to talk these things over before you get to that point.
The first thing I would look for is a reputable guide service above all else. Just because they will let you shoot long range does not mean they are a quality outfitter, may just mean that they do not care what happens to the game.
The reason most guides do not like long range shooting is because sadly, most hunters think they are long range shooters but in all honesty should be limited to less then 200 yards, especially when there is something like a bull yukon moose or grizzly in front of them.
Find a reputable outfitter first, talk about long range shooting later. You will have a better chance at getting your animals that way.
As far as your rifle, I would also have to agree with James that your running a little light with that rifle. For conventional ranges, it would work fine in most cases but again, this is a hunt of a lifetime.
Even if you do not want to jump up to the ultra mag cases, I would at least recommend something like a 300 Win Mag or 338 Win Mag. Both are very easy to shoot and both would be head and shoulders above what the 30-06 will offer on game at any range.
I would agree that the 300 RUM or 338 RUM or Edge would be better choices as well if you can shoot them accurately and with todays muzzle brakes
and recoil pads, there is no reason why you could not shoot them very well.
Again, putting that bullet in the right spot is the most critical factor to taking game but there is no doubt that the larger calibers are far more effective on heavy game when hit on the fringes. That said, a gut shot bear is a gut shot bear no matter what you hit him with so you need to be able to shoot what you take.
That is another reason guides do not like long range shooting, I would not like to go after a wounded grizzly either!!!