Yard work, I hate it!

We are about to enter our second summer since daddy's diagnosis.  Last summer presented a yard work challenge: Daddy wanted to do it.  At the beginning of the summer things were ok - we even still allowed the kids to ride with him on the riding lawn mower.  As the summer progressed (we're in the south and this year the summer pretty much extended to the end of October) we had to make some changes.  By mid-summer the kids were no longer allowed to ride with their papa; at the end they weren't even allowed to be outside if he was doing working.  We arrived at that decision when we noticed Daddy swinging around the bush cutter (picture a weed eater with a blade instead of string).  Every week some piece of lawn equipment would break which made daddy so angry at Sears' poor repair job and boy would he slander them (Sears never repaired any of the equipment).  At the time we didn't have the heart to take away this chore he loves to do, which also gives him a sense of pride.  In addition to doing mine and my parent's lawn care, he appointed himself yardman for his neighbors.  He'd weed eat or bush cut about half an acre back into the woods for his neighbors.  These sweet people knew about his disease and figured he wasn't doing any harm.  Though one older neighbor kept a keen eye on him - making sure he didn't undo all of her hard work.
By the end of summer my mama had paid who knows how much for the repairs from daddy's yardwork.  Both of our lawns had bald patches where daddy would weed eat in just one spot.  We looked forward to fall: when we could put away the equipment and have a much needed break.    Seasons change: so here we are, the grass is high and daddy's getting ready for yard work.  This year he has no business trying to use the bush cutter nor the riding lawn mower.  Already he's gotten upset, thinking my husband has borrowed his tools and not returned them - "what was he raised in a barn?"  The tools turned out to be in my parent's garage. 
So I feel like the bad guy - I'm suggesting that daddy start going every day to the adult facility, unless someone is home with him. 
This disease is crazy: in one moment I can chuckle at my daddy's determination to rid his loved one's yards of tall grass; and in the next moment I cry at his inability to do so - a task that was once so simple for him.