Let me say at the onset that I've driven a truck within sight of my stand-- probably inside 70 yards. I've gotten out, set a climber, gotten into the climber and then hunted successfully. Not only that, but I repeated the feat two years running and got two of my best bowkill bucks from this setup.
I don't think a parked ATV parked 100 yards out has that much of an effect on deer hunting. What DOES seem to have an effect is the noise of driving the contraption around in the woods. I frequently make jibes at the Orange Army-- those fellows who come out once a year on Opening Day and drive their ATVs around the hills surrounding my farm and do such a nice job of driving deer onto my property. It's true. It's all true. You can come out on Opening Day and listen. It's an absolute hoot. You have all these guys in orange vests and hats essentially acting as beaters for poor little old me.
I walk the half mile from the house out to my stand. I get there a good half hour earlier than the neighbors, and I get to listen to everyone crank up their ATVs and ride on out to their stands. On more than one occasion, I've heard deer crashing about in the woods a couple of hundred yards ahead of ATV. When I really see the effect is around 10 AM when everyone has enough and crank up their ATVs to come out. It can be an absolute free-for-all in the woods from 10 to 11 AM with machines running this way and that and deer running every which way trying to get out of the way. There are no machines running on my property, so the deer have a tendancy to all come over to my place.
My conclusion out of all this is that deer are not all that sensitive to the sight or stink of an ATV, but they are extremely sensitive to the sound and movement. If you need to drive an ATV, go in early, park well away and try to keep it all as quiet as possible.