So, background...
The house next door is occupied by an elderly woman. Her son lives about an hour away. He calls me once in a while when he needs someone to check on his mom...help her up if she falls, one time fix her TV remote (dead battery)... that kind of little stuff.
Another piece of background, I usually mow my lawn on Mondays.
Another piece of background. Sometime long ago (before me) someone decided they wanted the TV in a different place in the living room and did a really shoddy job routing a cable jumper outside, around the chimney, through the fence, through the front bushes, and back in on the other side of the fireplace.
Now, the events and the question...
On Saturday her son and grandson were up visiting/working on the place. They mowed her lawn, and I noticed today they mowed mine too. I also noticed they mowed it much shorter than I do (and here in the desert that can be hard on the grass), which contributed to the two mowed sprinklers I had to fix today. They also pushed the mower deep under the bushes to get the little scrappy weed/grass that grows under there, which contributed to me having to redo the cable jumper (which I knew needed to be done better anyway, but hadn't considered it a really high priority) because the movement of the bushes pulled one of the connectors loose.
So, I do appreciate the thought, and would like to say thanks or whatever...but I also really don't want them to do it again.
Any ideas how to not sound ungrateful here?