He was not that happy about doing it since it was pretty hot! But I think all dad's love the day when their kids can finally mow.
We have had a very hot and dry summer, so the grass is no longer full (I'm not going to have a $300 water bill just to keep my lawn green), but it was getting pretty long. He had mowed most of it and thought he was done, but I pointed out some spots he missed. That may be part of the reason for his expression....