The only grass I see is about 30 feet from the tree. I suspect it will be that way next year, too. You are best to use a ground cover plant. Ajuga, ivy, myrtle, pachysandra...whatever is the local favorite for this condition
Is this fescue? Bermuda?
You really have to butcher thse trees to get in enough sunlight--removing about 30 percent of the tree. I recommend never try to grow grass without 4 hours of direct sunlight per day.