Given my experience, I think 95h and others have given some good response here.  I doubt that getting grandpa to move to town to keep him from getting upset about seeing others working near the the day will help.  If he is anything like my father was, he will not be (or has not been) cooperative about moving, home health care, taking medication, using a life line, or anything else related to dealing with the illness.  In my dad's mind, the recent memories faded.  He insisted there was no reason why he should not be out there working.  As far as he was concerned, he was at the prime of his life and there was nothing wrong with him regardless of his location or medical condition.  At best, he accepted the idea that he was only having a brief illness and would be going back to the farm in a day or so. He thought I was the one with the problem.

Everyone is a little different, but I doubt that simply moving off the farm will help for very long if at all.  At that stage of the game, he will likely have a lot of difficulty making adjustments to new surroundings without the sort of support and control one would have in assisted living or a memory unit.

I tried to hold things together on the farm as long as I could, but I was the only immediate family left in the area.  Other relatives and the community in general really had no idea about how bad things were on a day to day basis.  Dad could look anyone in the eye and say everything was fine with a straight face.  Most everyone believed him, or at least believed things were not too bad.  This was years ago.  People knew about Alzheimers and dementia, but were not ready to accept the fact that it could turn what was once a fine upstanding man into someone totally irresponsible and a danger to himself and others.  People (who ought to have known better) were a lot more inclined to believe I was just a spoiled son trying to kick the old man off the farm.  Some went to a considerable amount of trouble to interfer in the process of getting medical help.  The experience taught me to move on with what was left of my life and not to expect others to apologize or try to make things right.  Some people just are what they are.

I hope you get all the support you need from friends and family as you deal with this.  Just keep in mind that some of those who are closest and in the best position to help might not be strong enough to face up to reality.  They could turn on you instead of being helpful and supportive.  They have the luxury of not facing up to reality.  You do not.