I agree 100%. I would not worry about getting out to 1000 yards. This will be my 31st season hunting and I have never taken a shot on any animal that could not have been taken well inside of 1,000 yards.
That 6.5 Creedmoor will do the trick for certain. That 156 grain Berger loaded at 2660 fps should be humming along at over 1700fps and over 1000 pounds of energy at 800 yards. That makes it a legitimate hunting round at 800 yards if you do your part.
For the recoil generated, you aren't going to get better performance.
The 300 Win Mag with the 210 grain Bergers is traveling almost 1800 fps and has just over a frog's hair more than 1500 pounds of energy at the same distance. Is the extra recoil worth it for your dad?
You can obviously look into muzzle breaks for the Win Mag and tame the felt recoil a little bit. You could also do the same for the Creedmoor and make the thing a real puppy dog behind the scope.
Its up to you, but if recoil were an issue (and if my ol' man were still alive it would be) I would go with the Creedmoor. Also, I would look at the premier rifle instead of the HMR. I believe that the HMR comes with a 22" pipe in the 6.5 CM. You get a few more features and a few more inches with the premier for just a few dollars more.